Who needs a glucose tolerance test and why

Scientific editor: M. Merkushev, PSPbGMU im. Acad. Pavlova, medical business.
January 2019


Synonyms: Oral glucose tolerance test, GTT, glucose tolerance test, sugar curve, Glucose tolerance test (GTT)

The glucose tolerance test is a laboratory analysis that determines the plasma glucose level on an empty stomach and 2 hours after a carbohydrate load. The study is carried out twice: before and after the so-called "load".

The glucose tolerance test allows you to evaluate a number of important indicators that determine whether a patient has a serious prediabetic state, impaired glucose tolerance or diabetes mellitus.

General information

Glucose is a simple carbohydrate that is ingested with ordinary foods and absorbed into the bloodstream in the small intestine. It is she who provides the nervous system, the brain and other internal organs and systems of the body with vital energy. For normal health and good productivity, glucose levels must remain stable. Pancreatic hormones: insulin and glucagon regulate its level in the blood. These hormones are antagonists - insulin lowers sugar levels, and glucagon, on the contrary, increases it.

Initially, the pancreas produces a proinsulin molecule, which is divided into 2 components: insulin and C-peptide. And if insulin after secretion remains in the blood for up to 10 minutes, then the C-peptide has a longer half-life - up to 35-40 minutes.

On a note: until recently, it was believed that the C-peptide has no value for the body and does not perform any functions. However, the results of recent studies have revealed that C-peptide molecules have specific receptors on the surface that stimulate blood flow. Thus, the determination of the level of C-peptide can be successfully used to detect hidden disorders of carbohydrate metabolism.

An endocrinologist, a nephrologist, a gastroenterologist, a pediatrician, a surgeon, and a therapist can issue a referral for analysis.

A glucose tolerance test is prescribed in the following cases:

  • glucosuria (increased sugar in the urine) in the absence of symptoms of diabetes mellitus and with a normal level of glucose in the blood,
  • clinical symptoms of diabetes, but blood sugar and urine are normal,
  • examination of patients with risk factors for diabetes:
    • over 45 years old
    • BMI body mass index of more than 25 kg / m 2,
    • arterial hypertension,
    • violation of lipid metabolism,
  • hereditary predisposition to diabetes,
  • determination of insulin resistance in obesity, metabolic disorders,
  • glucosuria against the background of other processes:
    • thyrotoxicosis (increased secretion of thyroid hormones of the thyroid gland),
    • liver dysfunction
    • urinary tract infections
    • pregnancy
  • the birth of large children weighing more than 4 kg (analysis is carried out both to the woman in labor and to the newborn),
  • prediabetes (in the case when preliminary blood biochemistry for glucose showed an intermediate result of 6.1-7.0 mmol / l),
  • a pregnant patient is at risk of developing diabetes mellitus (the test is usually performed in the 2nd trimester).
  • chronic periodontosis and furunculosis
  • long-term use of diuretics, glucocorticoids, synthetic estrogens

GTT is also given to patients with sensory neuropathy in conjunction with a vitamin B12 test for the differential diagnosis of diabetic neuropathy and other types of neuropathies 1.

On a note: of great importance is the level of C-peptide, which allows us to assess the degree of functioning of cells secreting insulin (islets of Langerhans). Thanks to this indicator, the type of diabetes mellitus is determined (insulin-dependent or independent) and, accordingly, the type of therapy used.

The oral glucose tolerance test allows you to diagnose various disorders of carbohydrate metabolism, such as diabetes mellitus, impaired glucose tolerance, fasting glycemia, but cannot allow you to clarify the type and causes of diabetes mellitus, and therefore, after obtaining any result, it is advisable to conduct an additional examination 2:

When to perform GTT

AgeHealth statusPeriodicity
over 45 years old
  • normal body weight
  • lack of risk factors
  • 1 time in 3 years with a normal result
over 16 years old
  • the presence of one of the risk factors
  • body mass index over 25 kg / m 2
  • 1 time in 3 years with a normal result
  • Once a year for deviations from the norm

How to calculate BMI

BMI = (mass, kg): (height, m) 2

Cases where a glucose tolerance test is not performed

GTT is not advisable in the following cases

  • a recent heart attack or stroke,
  • recent (up to 3 months) surgical intervention,
  • the end of the 3rd trimester in pregnant women (preparation for childbirth), childbirth and the first time after them,
  • preliminary blood biochemistry showed a sugar content of more than 7.0 mmol / L.
  • against the background of any acute disease, including infectious.
  • while taking drugs that increase the level of glycemia (glucocorticoids, thyroid hormones, thiazides, beta-blockers, oral contraceptives).

Normal GTT Values

4.1 - 7.8 mmol / L

Glucose after 60 minutes after glucose load

4.1 - 7.8 mmol / L

Glucose after 120 minutes after glucose load

On the eve of the test and on the day of its conduct, it is forbidden to take alcohol and narcotic / potent drugs,

Also, it is necessary to protect yourself from any physical and psycho-emotional stress per day.

Features

All current or recently completed treatment courses must be reported to the doctor in advance.

The examination is not carried out in the acute period of infectious and inflammatory processes (a false-positive result is possible),

The analysis does not give up immediately after other studies and procedures (x-ray, CT, ultrasound, fluorography, physiotherapy, massage, rectal examination, etc.),

The female menstrual cycle can affect the concentration of sugar, especially if the patient has impaired carbohydrate metabolism.

How are glucose tolerance tests performed?

GTT is prescribed exclusively provided that the result of a biochemical study of the fasting blood glucose level is not more than 7.0 mmol / L. If this rule is ignored, the risk of hyperglycemic coma in a diabetic is increased.

In addition, in the case of a persistent increase in sugar in the venous blood of more than 7.8 mmol / l, the doctor has the right to make a diagnosis of diabetes without the appointment of additional examinations. The glucose tolerance test, as a rule, is not performed for children under 14 years of age (with the exception of the examination of newborns according to indications).

On the eve of GTT, blood biochemistry is performed and the total blood sugar level is detected,

The glucose tolerance test is scheduled for the morning (from 8.00 to 11.00). The biomaterial for the study is venous blood, which is taken by venipuncture from the cubital vein,

Immediately after blood sampling, the patient is invited to drink a glucose solution (or it is administered intravenously),

After 2 hours, which is recommended to be carried out in complete physical and emotional rest, a repeated blood sampling is performed. Sometimes the analysis is carried out in several stages: after the first half hour, and then after 2-3 hours.

It is important to know! In the process of glucose tolerance test and / or after it, mild nausea may appear, which can be eliminated by resorption of a slice of lemon. This product will not affect glucose levels, but will help kill the sugary taste in your mouth while taking the sweet solution. Also, after repeated blood sampling, the head may feel a little dizzy, a feeling of severe hunger may appear, which is associated with the active production of insulin. After the test, you must immediately have a snack savory and hearty dishes.

Types of glucose tolerance tests: oral, intravenous

Glucose tolerance means how quickly and efficiently released insulin can carry it into cells. This sample mimics a meal. The main route of glucose intake is oral. The patient is given a sweet solution to drink and glycemia (blood sugar) is measured before and after administration.

Intolerance to a saturated drink with glucose is extremely rare, then the desired dose (75 g) can be injected into a vein. Usually, this is a study with severe toxicosis in pregnant women, vomiting, malabsorption in the intestines.

And here is more about contra-hormonal hormones.

Indications for

The doctor issues a referral for analysis if diabetes is suspected. The patient may have complaints about:

  • Great thirst, increased urine output.
  • A sharp change in body weight.
  • Attacks of hunger.
  • Constant weakness, fatigue.
  • Drowsiness during the day, after eating.
  • Itchy skin, acne, boils.
  • Hair loss.
  • Recurrent thrush, itching in the perineum.
  • Slow healing of wounds.
  • The appearance of spots, points in front of the eyes, a decrease in visual acuity.
  • Weakening of sexual desire, erection.
  • Menstrual irregularities.
  • Gum disease, loose teeth.

As a rule, the test is recommended for the latent course of the disease, which is typical for type 2 diabetes. To detect disorders of carbohydrate metabolism, a sample with a sugar load is indicated for patients with:

  • Obesity.
  • Metabolic syndrome (hypertension, insulin resistance, high weight).
  • Risk factors for developing diabetes: heredity, age from 45 years, the predominance of sweets and fatty foods in the diet, smoking, alcoholism.
  • Early atherosclerosis: angina pectoris, hypertension, circulatory disorders in the brain or limbs.
  • Polycystic ovary.
  • Gestational diabetes in the past.
  • The need for long-term treatment with analogues of thyroid hormones or adrenal glands.

Glucose tolerance test

Glucose tolerance test (GTT) or glucose tolerance test are specific examination methods that help to identify the body's attitude to sugar. With its help, a tendency to diabetes, suspicions of a latent disease is determined. Based on indicators, you can intervene in time and eliminate threats. There are two types of tests:

  1. Oral glucose tolerance or oral - sugar load is carried out a few minutes after the first blood sampling, the patient is asked to drink sweetened water.
  2. Intravenous - if it is impossible to independently use water, it is administered intravenously. This method is used for pregnant women with severe toxicosis, patients with gastrointestinal disorders.

How to take a glucose tolerance test

If the doctor suspects one of the diseases mentioned above, he gives a referral for glucose tolerance analysis. This examination method is specific, sensitive and "moody." It should be carefully prepared for it, so as not to get false results, and then, together with the doctor, choose a treatment to eliminate the risks and possible threats, complications during diabetes mellitus.

Preparation for the procedure

Before the test, you need to carefully prepare. Preparation measures include:

  • a ban on alcohol for several days,
  • you must not smoke on the day of analysis,
  • tell the doctor about the level of physical activity,
  • don’t eat sweet food per day, don’t drink a lot of water on the day of analysis, follow a proper diet,
  • take stress into account
  • do not take a test for infectious diseases, postoperative condition,
  • for three days, stop taking medications: sugar-lowering, hormonal, stimulating metabolism, depressing the psyche.

Contraindications

The results of the study may be unreliable against the background of concomitant diseases or, if necessary, the use of medications that can change the level of glucose. It is impractical to diagnose if:

  • Acute inflammatory process.
  • Viral or bacterial infection with fever.
  • Exacerbations of peptic ulcer.
  • Acute or subacute circulatory disorders, in the first month after a heart attack, stroke, surgery or injury, childbirth.
  • Cushing's disease (syndrome) (increased secretion of cortisol).
  • Gigantism and acromegaly (excess growth hormone).
  • Pheochromocytomas (adrenal gland tumor).
  • Thyrotoxicosis.
  • Stress overvoltage.
  • Previously diagnosed type 1 or type 2 diabetes mellitus, a blood test for glycated hemoglobin and glycemic control before and after meals are used to control its course.

Preparations that change the results of the glucose tolerance test include: diuretics, beta-blockers, anticonvulsants and hormones. Women during menstruation need to abandon the diagnosis, transfer the test to the 10-12th day of the cycle.

Preparation for delivery

Before the study, patients are recommended a preparatory period. It is important in order to minimize the errors associated with nutrition and lifestyle. Proper preparation includes:

  • For at least 3 days, you must observe the usual diet and physical activity.
  • Carbohydrates can not be completely excluded from the diet, but their excessive amount should also be discarded, the optimal content in the menu is 150 g.
  • It is contraindicated to start a diet or overeat a week before the day of the examination.
  • For 10-14 hours it is forbidden to take food, alcohol, coffee or juice.
  • In the morning before the diagnosis, you can drink a glass of water without additives.
  • It is not recommended to exercise, smoke, get nervous before the test.
In the morning, before a diagnosis, you can drink a glass of water without additives.

How is the analysis

The examinee must come to the laboratory in advance in order to rest for about 20-30 minutes, observing physical and mental peace. Then he measured the blood sugar (an indicator of glycemia). After that, you need to drink a glucose solution. Subsequently, measurements are taken every 30 minutes for 2 hours. The results are used to construct the glycemic curve.

Dates of glucose tolerance test in pregnant women

During the period of gestation, the endocrine system, like the whole body, is rebuilt. In patients with risk factors, the chances of developing a gestational form of diabetes are doubled. These include:

  • Cases of any form of diabetes in the family.
  • Obesity.
  • Viral infections in the early stages.
  • Pancreatitis
  • Polycystic ovary.
  • Smoking, alcoholism.
  • A burdened obstetric history: the birth of a large fetus in the past, gestational diabetes, stillbirth, developmental abnormalities in previously born children.
  • Monotonous diet with excess carbohydrates.

Pregnant women who have at least one of these factors require a glucose tolerance test starting from the 18th week of pregnancy. For everyone else, it is also included in the compulsory complex, but for a period from the 24th to the 28th week. A feature of the gestational variant of diabetes is a normal fasting glucose level and its increase after eating (glucose intake) more than 7.7 mmol / L.

Norm in results

After taking the solution, the sugar from the initial level increases to a maximum in an hour, and then by the end of the second hour it decreases to normal values. With diabetes, there is no such decrease. In the case of an intermediate condition called impaired carbohydrate tolerance (prediabetes), glucose drops after exercise, but does not reach normal values.

Glucose tolerance test results

Deviation Options

The highest diagnostic value is the increase in glycemia. According to the test results, diabetes and impaired carbohydrate tolerance can be detected.Also, in recent stressful situations, acute diseases, injuries, a false-positive result may occur. In case of doubt in the diagnosis, it is recommended to repeat the test after 2 weeks and pass the following tests:

  • Blood for the content of insulin and proinsulin, a common protein.
  • Blood biochemistry with a lipid profile.
  • Urinalysis for glucose.
  • Glycated hemoglobin.
Urine glucose test

With prediabetes and overt diabetes, diet with minimal carbohydrate minimization is recommended. This means that sugar, white flour and all products with their content should be completely excluded from the diet. Due to concomitant impairment of fat metabolism, animal fats should be limited. The minimum physical activity is 30 minutes a day for at least 5 days a week.

A decrease in glucose is most often the result of improper selection of a dose of insulin or tablets for diabetes. In some cases, this is facilitated by diseases of the intestines, pancreas, chronic infections, severe liver diseases, alcohol intake.

And here is more about diabetes in children.

The glucose tolerance test mimics a meal. Measurements of glucose reflect how carbohydrates are absorbed by the body's own insulin. It is prescribed both for diabetes symptoms and for patients at risk. Reliability requires preparation. Based on the results, a change in diet, physical activity, and the use of medications are recommended.

Names of the glucose tolerance test (oral glucose tolerance test, 75 g glucose test, glucose tolerance test)

At present, the name of the glucose tolerance test (GTT) method is generally accepted in Russia. However, in practice other names are also used to denote the same laboratory diagnostic methodwhich are inherently synonymous with the term glucose tolerance test. Such synonyms for the term GTT are the following: oral glucose tolerance test (OGTT), oral glucose tolerance test (PHTT), glucose tolerance test (TSH), as well as a test with 75 g of glucose, a sugar load test, construction of sugar curves. In English, the name of this laboratory method is indicated by the terms glucose tolerance test (GTT), oral glucose tolerance test (OGTT).

What shows and why is a glucose tolerance test necessary?

So, the glucose tolerance test is a determination of the level of sugar (glucose) in the blood on an empty stomach and two hours after taking a solution of 75 g of glucose dissolved in a glass of water. In some cases, an extended glucose tolerance test is carried out, in which the blood sugar level is determined on an empty stomach, 30, 60, 90 and 120 minutes after using a solution of 75 g of glucose.

Normally, fasting blood sugar should fluctuate between 3.3 - 5.5 mmol / L for blood from a finger, and 4.0 - 6.1 mmol / L for blood from a vein. An hour after a person drinks 200 ml of a liquid in an empty stomach, in which 75 g of glucose is dissolved, the blood sugar level rises to a maximum level (8 - 10 mmol / l). Then, as the glucose received is processed and absorbed, the blood sugar level decreases, and 2 hours after ingestion, 75 g of glucose comes to normal, and is less than 7.8 mmol / l for blood from a finger and vein.

If two hours after taking 75 g of glucose, the blood sugar level is above 7.8 mmol / L, but below 11.1 mmol / L, this indicates a latent violation of carbohydrate metabolism. That is, the fact that carbohydrates in the human body are absorbed with disorders is too slow, but so far these disorders are compensated and proceed secretly, without visible clinical symptoms. In fact, the abnormal value of blood sugar two hours after taking 75 g of glucose means that a person is already actively developing diabetes, but he has not yet acquired a classic expanded form with all the characteristic symptoms. In other words, the person is already sick, but the stage of the pathology is early, and therefore there are no symptoms yet.

Thus, it is obvious that the value of the glucose tolerance test is huge, since this simple analysis allows you to identify the pathology of carbohydrate metabolism (diabetes mellitus) at an early stage, when there are still no characteristic clinical symptoms, but then you can treat and prevent the formation of classical diabetes. And if the latent disorders of carbohydrate metabolism, which are detected using the glucose tolerance test, can be corrected, reversed and prevent the development of the disease, then at the stage of diabetes, when the pathology is already fully formed, it is already impossible to cure the disease, but it is only possible to artificially maintain the normal level of sugar medication in the blood, delaying the appearance of complications.

It should be remembered that the glucose tolerance test allows early detection of latent disorders of carbohydrate metabolism, but does not make it possible to distinguish between the first and second types of diabetes mellitus, as well as the causes of the development of pathology.

Given the importance and diagnostic information content of the glucose tolerance test, this analysis is justified to perform when there is suspicion of a latent violation of carbohydrate metabolism. Signs of such a latent carbohydrate metabolism disorder are as follows:

  • Blood sugar levels are above normal, but below 6.1 mmol / L for blood from a finger and 7.0 mmol / L for blood from a vein,
  • The periodic appearance of glucose in the urine against a background of normal blood sugar,
  • Great thirst, frequent and profuse urination, as well as increased appetite against a background of normal blood sugar,
  • The presence of glucose in the urine during pregnancy, thyrotoxicosis, liver disease or chronic infectious diseases,
  • Neuropathy (disruption of the nerves) or retinopathy (disruption of the retina) with unclear causes.

If a person has signs of latent disorders of carbohydrate metabolism, then he is recommended to do a glucose tolerance test to make sure the presence or absence of an early stage of the pathology.

Absolutely healthy people who have normal blood sugar levels and have no signs of impaired carbohydrate metabolism do not need to do a glucose tolerance test, since it is completely useless. Also, it is not necessary to do a glucose tolerance test for those who already have fasting blood sugar levels that correspond to diabetes mellitus (more than 6.1 mmol / L for blood from a finger and more than 7.0 for blood from a vein), since their disorders are quite obvious, not hidden.

Indications for glucose tolerance test

So, a glucose tolerance test is necessarily indicated for execution in the following cases:

  • Doubtful results of fasting glucose determination (below 7.0 mmol / l, but above 6.1 mmol / l),
  • Accidentally detected increase in blood glucose levels due to stress,
  • Accidentally detected presence of glucose in the urine against a background of normal blood sugar and the absence of symptoms of diabetes mellitus (increased thirst and appetite, frequent and profuse urination),
  • The presence of signs of diabetes against a background of normal blood sugar,
  • Pregnancy (to detect gestational diabetes)
  • The presence of glucose in the urine amid thyrotoxicosis, liver disease, retinopathy, or neuropathy.

If a person has any of the above situations, then he should definitely pass a glucose tolerance test, since there is a very high risk of a latent course of diabetes. And it is precisely to confirm or refute such latent diabetes mellitus in such cases that a glucose tolerance test is performed, which allows you to "reveal" an imperceptible violation of carbohydrate metabolism in the body.

In addition to the above required indications, there are a number of situations in which it is advisable for people to regularly donate blood for a glucose tolerance test, since they have a high risk of developing diabetes. Such situations are not mandatory indications for taking a glucose tolerance test, but it is highly advisable to periodically perform this analysis in order to detect prediabetes or latent diabetes in a timely manner at an early stage.

Similar situations in which it is recommended to periodically take a glucose tolerance test include the presence of the following diseases or conditions in a person:

  • Over 45 years old
  • Body mass index more than 25 kg / cm 2,
  • The presence of diabetes in parents or blood siblings,
  • Sedentary lifestyle,
  • Gestational diabetes in past pregnancies,
  • The birth of a child with a body weight of more than 4.5 kg,
  • Preterm birth, giving birth to a dead fetus, miscarriage in the past,
  • Arterial hypertension,
  • HDL levels below 0.9 mmol / L and / or triglycerides above 2.82 mmol / L,
  • The presence of any pathology of the cardiovascular system (atherosclerosis, coronary heart disease, etc.),
  • Polycystic ovary,
  • Gout,
  • Chronic periodontal disease or furunculosis,
  • Reception of diuretics, glucocorticoid hormones and synthetic estrogens (including as part of combined oral contraceptives) for a long period of time.

If a person does not have any of the above conditions or diseases, but his age is older than 45 years, then he is recommended to take a glucose tolerance test once every three years.

If a person has at least two conditions or diseases from the above, then he is recommended to take a glucose tolerance test without fail. If at the same time the test value turns out to be normal, then it must be taken as part of a preventive examination every three years. But when the test results are not normal, then you need to carry out the treatment prescribed by your doctor and take an analysis once a year to monitor the condition and progression of the disease.

After glucose tolerance test

When the glucose tolerance test is completed, you can have breakfast with whatever you want, drink, and also return to smoking and drinking alcohol. In general, glucose loading usually does not cause a deterioration in well-being and does not adversely affect the state of reaction rate, and therefore, after a glucose tolerance test, you can do any of your business, including working, driving a car, studying, etc.

Glucose tolerance test results

The result of the glucose tolerance test is two numbers: one is the fasting blood sugar level, and the second is the blood sugar value two hours after taking the glucose solution.

If an extended glucose tolerance test was performed, the result is five numbers. The first digit is the fasting blood sugar value. The second digit is the blood sugar level 30 minutes after ingestion of glucose solution, the third digit is the sugar level one hour after ingestion of glucose solution, the fourth digit is blood sugar after 1.5 hours, and the fifth digit is blood sugar after 2 hours.

The obtained blood sugar values ​​on an empty stomach and after taking a glucose solution are compared with normal, and a conclusion is made about the presence or absence of a pathology of carbohydrate metabolism.

Glucose tolerance test rate

Normally, fasting blood glucose is 3.3 - 5.5 mmol / L for blood from a finger, and 4.0 - 6.1 mmol / L for blood from a vein.

The blood sugar level two hours after taking the glucose solution is normally less than 7.8 mmol / L.

Half an hour after taking the glucose solution, blood sugar should be lower than an hour, but higher than on an empty stomach, and should be about 7-8 mmol / L.

The blood sugar level one hour after taking the glucose solution should be the highest, and should be about 8 - 10 mmol / L.

The sugar level after 1.5 hours after taking the glucose solution should be the same as after half an hour, that is, about 7 - 8 mmol / L.

Decoding glucose tolerance test

Based on the results of the glucose tolerance test, the doctor can make three conclusions: norm, prediabetes (impaired glucose tolerance) and diabetes mellitus. The values ​​of sugar levels on an empty stomach and two hours after taking a glucose solution, corresponding to each of the three options for conclusions, are shown in the table below.

The nature of carbohydrate metabolismFasting blood sugarBlood sugar two hours after taking glucose solution
Norm3.3 - 5.5 mmol / L for finger blood
4.0 - 6.1 mmol / L for blood from a vein
4.1 - 7.8 mmol / L for finger and vein blood
Prediabetes (impaired glucose tolerance)Less than 6.1 mmol / L for finger blood
Less than 7.0 mmol / L for blood from a vein
6.7 - 10.0 mmol / L for finger blood
7.8 - 11.1 mmol / L for blood from a vein
DiabetesMore than 6.1 mmol / L for finger blood
More than 7.0 mmol / L for blood from a vein
More than 10.0 mmol / L for finger blood
More than 11.1 mmol / L for blood from a vein

To understand what result this or that particular person received according to the glucose tolerance test, you need to look at the scope of sugar levels that his analyzes fall into. Next, see what (normal, prediabetes or diabetes) refers to the scope of the values ​​of sugar, which fell into their own analyzes.

Where is the glucose tolerance test done?

The glucose tolerance test is performed in almost all private laboratories and in laboratories of ordinary public hospitals and clinics. Therefore, to make this study is simple - just go to the laboratory of a state or private clinic. However, state laboratories often do not have glucose for testing, and in this case you will need to buy glucose powder on your own at the pharmacy, bring it with you, and medical staff will make a solution and perform the test. Glucose powder is usually sold in public pharmacies, which have a prescription department, and in private pharmacy chains it is practically absent.

Classification of glucose tolerance techniques

Schematically, all presented clinical trial formats will be divided into two camps. The first includes the oral approach, which is simply denoted by the letters PGTT for shortening. According to the identical principle they designate the oral method, abbreviating its names to ONTT.

The second category provides for intravenous modification. But, regardless of how the sampling of biological material is carried out for subsequent study in the laboratory, the preparatory rules remain almost unchanged.

The difference between the two types is the route of carbohydrate administration. This is a glucose load, which is performed a few minutes after the first stage of blood sampling. In the oral version, the preparation requires the use of a clearly calculated dose of glucose inside. The doctor will be able to say exactly how many milliliters will be required after a detailed assessment of the current condition of the victim.

In the intravenous approach, an injection format is used. In this case, the dosage is calculated according to the same algorithm. But this version is of little demand among doctors because of the relative complexity. They resort to it only in situations where the victim is not able to independently drink well-sweetened water in advance.

Most often, such a radical measure will be needed if a person is in an extremely serious condition. The same applies to pregnant women, which show clear signs of severe toxicosis. This solution is suitable for those who have some kind of disturbance in the normal activity of the gastrointestinal tract.

So, with a diagnosed illness regarding the impossibility of normal absorption of substances in the process of nutritional metabolism, one cannot do without an intravenous glucose load.

The price of two varieties of the procedure is not much different from each other. All the same, the patient is often asked to bring a glucose reserve with him.

Medical indications

Having figured out what they are doing this analysis for, people are starting to wonder why they should undergo such a specific examination if they don’t suffer from diabetes. But even a suspicion of it or a poor hereditary predisposition can become the reasons for regular passage of research from a doctor.

If the therapist considered it necessary to give a direction for diagnosis, then abandoning it simply because of fear or the opinion that this is an extra waste of time is a bad idea. Just like that, doctors of their wards will not succumb to glucose load.

Often, a prescription is prescribed by district doctors with characteristic diabetic symptoms, or gynecologists, endocrinologists.

The group of those who are most likely to be prescribed directions included those patients who:

  • Type 2 diabetes is suspected and a more accurate diagnosis is required.
  • for the first time, they are prescribing or reviewing the current course of drug treatment associated with a diagnosed "sugar disease",
  • you need to analyze the dynamics of recovery in order to exclude the possibility of a complete lack of effect,
  • they suspect a first degree of diabetes,
  • regular self-monitoring is required,
  • suspected gestational type of diabetes, or after actual detection for subsequent monitoring of health status,
  • prediabetic condition
  • there are malfunctions in the functioning of the pancreas,
  • deviations in the adrenal glands are recorded.

No less often, the reason for sending to the diagnostic room is a confirmed metabolic syndrome. As evidenced by the reviews of some victims, they were poisoned to undergo a test for diseases associated with hepatic activity or ailments caused by malfunctions of the pituitary gland.

It is not without verification of this kind if a person has found a violation of glucose tolerance. You can meet in the queue for blood donation just people suffering from various degrees of obesity. Nutritionists send them there in order to further build an individual program of rational nutrition and physical activity.

If during the study of the hormonal composition of the body with the suspicion of endocrine abnormalities, it turns out that the local indicators are far from the norm, then without a glucose tolerance method the final verdict will not be issued. As soon as the diagnosis is officially confirmed, you will have to come to the diagnostic room on an ongoing basis. This will allow you to conduct self-control for insurance impairment.

Due to the fact that not all inhabitants know where to take such a test, they turn to pharmacists with a request to purchase portable biochemical analyzers. But experts remind that the initial method is still worth starting with a detailed result obtained in laboratory tests.

But for self-monitoring, mobile glucometers are a great idea. Almost any pharmacy can offer several options from global manufacturers whose models differ in functionality.

But here, too, has its own nuances:

  • home appliances only analyze whole blood,
  • they have a greater margin of error than stationary equipment.

Against this background, it becomes clear that one cannot completely refuse trips to the hospital. Based on the officially documented information received, the doctor will then decide on the correction of the therapeutic program. Therefore, if before buying a portable device, a person can still think about whether such a step is necessary or not, then this does not happen with a hospital examination. It is necessary to review a previously approved treatment program.

For home use, the simplest devices will fit perfectly. They are able to not only detect the level of glycemia in real time. Their responsibilities include calculating the volume of glycated hemoglobin, which on the screen of the device will be marked with the designation "HbA1c".

Medical contraindications

Despite the fact that for most patients the analysis does not pose any threat, it nevertheless has several significant contraindications. Among them, in the first place is the individual intolerance of the active substance, which can provoke a strong allergic reaction. In the most sad scenario, this culminates in an almost instant anaphylactic shock.

Among other phenomena and conditions that pose a potential danger during glucose tolerance studies, note:

  • diseases associated with the gastrointestinal tract, which most often covers an exacerbation of the chronic course of pancreatitis,
  • acute stage of the inflammatory process,
  • an untreated infectious lesion of any genesis that spoils the reliability of the clinical picture,
  • toxicosis with a strong manifestation of it,
  • postoperative period.

Separately considered are the cases of victims who should, for some reason, observe bed rest. Such a ban is more relative, which means that it is possible to conduct a survey if its benefits are superior to harm.

The final decision is made by the attending physician according to the circumstances.

Procedure Algorithm

Manipulation itself is not particularly difficult to implement. The problem is only the duration, since you have to spend about two hours. The reason that affects such a long time is the inconsistency of glycemia. Here it is also necessary to take into account the pancreatic gland performance, which is not functioning in all applicants.

The scheme of how the testing is done includes three stages:

  • fasting blood sampling
  • glucose load
  • re-fence.

The first time blood is collected after the victim has not taken food for at least 8 hours, otherwise the reliability will be smeared. Another problem is over-preparation, when a person literally starves himself on the eve of the day before.

But if the last meal was more than 14 hours ago, then this turns the selected biological material into unsuitable for further study in the laboratory. Because of this, it is most productive to go to the reception early in the morning, not eating anything for breakfast.

At the stage of glucose loading, the victim must either drink the prepared “syrup” or take it by injection. If the medical staff gave preference to the second method, then they take a 50% glucose solution, which has to be administered slowly for about three minutes. Sometimes the victim is diluted with a solution of 25 grams of glucose. A slightly different dosage is seen in children.

With alternative methods, when the patient is able to take the “syrup” by himself, 75 grams of glucose are diluted in 250 ml of warm water. For pregnant women and children, the dosage varies. If a woman practices breastfeeding, then you should also consult with an expert in advance.

Particularly noteworthy are people who suffer from bronchial asthma or angina pectoris. It’s easier for them to consume 20 grams of fast carbohydrates. The same goes for those who have suffered a stroke or heart attack.

As a basis for the solution, the active substance is taken not in ampoules, but in powder. But even after the consumer finds it in the pharmacy in the right amount, it is strictly forbidden to independently carry out the glucose load at home. This can lead to serious complications.

The final stage involves the re-sampling of biological material. Moreover, they will do this several times within one hour. This is a necessary measure aimed at determining the natural fluctuations in the composition of the blood. Only when comparing several results will it be possible to outline the widest possible clinical picture.

The verification mechanism is based on the action of carbohydrate metabolism. The faster the components of the “syrup” entering the body are consumed, the sooner the pancreas copes with them. When it turns out that the “sugar curve” after exposure to carbohydrates continues all the next few samples to stay at almost the same level, then this is a bad sign.

In the best case, this indicates prediabetes, which needs emergency treatment so as not to develop into a stage when insulin in exorbitant amounts becomes the norm.

But experts recall that even a positive answer is not a reason to panic. Anyway, for any deviations from the norm, you will have to re-test. Another key to success should be the correct decryption, which is better to entrust to an experienced endocrinologist with experience.

If, even repeated repeated attempts, I demonstrate an identical result, the doctor can send the victim to undergo an adjacent diagnosis. This will accurately determine the source of the problem.

Norm and deviations

The most important point for decoding should be the fact of which particular blood was taken for study. It could be:

The difference will be based on whether whole blood or only its components were used, which were extracted from the vein during plasma separation. The finger is taken according to a typical protocol: a finger is pierced with a needle and the right amount of material is taken for biochemical analysis.

Everything is much more complicated when sampling material from a vein. Here, the first dose is usually placed in a cold test tube. The ideal option is the vacuum version, which provides optimal conditions for subsequent storage.

Special preservatives are added to the medical container in advance. They are designed to save the sample without changing its structure and composition, which protects the blood from the impurity of excess components.

Sodium fluoride is usually used as a preservative. Dosage is calculated according to the standard template. Its main task is to slow down the enzymatic processes. And sodium citrate, which is also labeled with the EDTA mark, is the guardian of coagulability.

After the preparatory stage, the test tube is sent to ice in order to prepare medical equipment to help separate the contents into separate components. Since only plasma will be required for laboratory testing, laboratory assistants use a special centrifuge where biological material is placed.

Only after all this long chain of preparation, the selected plasma is sent to the department for further study. The most important thing for a given stage is to have time to invest in a half-hour interval. Exceeding the established limits threatens the subsequent distortion of reliability.

Next comes the direct evaluation phase, where the glucose-osmidase method usually appears. Its “healthy” borders must fit into the range from 3.1 to 5.2 mmol / liter.

Here, enzymatic oxidation, where glucose oxidase appears, is taken as the basis. The output is hydrogen peroxide. Initially, colorless components, when exposed to peroxidase, get a bluish tint. The brighter the characteristic hue is expressed, the more glucose is found in the collected sample.

The second most popular is the orthotoluidine approach, which provides standard indicators in a radius of 3.3 to 5.5 mmol / liter. Here, instead of the oxidizing mechanism, the principle of behavior in an acidic environment is triggered. The color intensity is due to the influence of an aromatic substance derived from ordinary ammonia.

As soon as a specific organic reaction is triggered, glucose aldehydes begin to oxidize. As the basis for the final information, take the color saturation of the resulting solution.

Most medical centers prefer this method, since they consider it the most accurate. Not in vain, after all, it is he who is preferred when acting under the protocol for GTT.

But even if we discard these two most demanded approaches, there are still a few colometric varieties and enzymatic variations. Although they are used less frequently, they are not much different in terms of information content from popular alternatives.

In home analyzers, special strips are used, and in mobile devices, electrochemical technologies are taken as a basis. There are even instruments where several strategies are mixed to provide the most complete data.

Watch the video: My Glucose Screening- Checking for Gestational Diabetes In Pregnancy (March 2020).