Laboratory blood tests help to quickly and reliably determine the presence of serious diseases in the human body and prescribe adequate treatment. Many diabetics are familiar with such a test as a blood test for glycated hemoglobin.
Hemoglobin is a special protein; it is a component of the proteins of living organisms that have a circulatory system. By binding to oxygen molecules, hemoglobin brings it into the blood cells and takes part in the evacuation of carbon dioxide from tissues. Today, several types of hemoglobin are known, among them hemoglobin A predominates, accounting for about 95% of all hemoglobin in the blood. A-hemoglobin, in turn, is divided into components, one of them is called A1c.
Hemoglobin forms irreversible bonds with glucose; doctors call this process the Maillard reaction, glycation or glycation. Therefore, if hemoglobin has come into contact with glucose, it is called glycated. Endocrinologists consider this substance to be the main assistant in diagnosing diabetes mellitus and other carbohydrate metabolism disorders.
The lower the blood glucose level, the slower the glycation process occurs. The average duration of red blood cell activity is about three months, meaning that glucose levels in the bloodstream can only be monitored over this period of time. In other words, the analysis for glycated hemoglobin is a kind of indicator of the degree of “sugarification” of the blood.
What is HbA1c
Glycosylated hemoglobin is a special biochemical characteristic that is a reflection of the average amount of blood sugar over the previous three months.
Hemoglobin is a protein found in red blood cells.
When exposed to glucose for a long time, it turns into a compound called glycated hemoglobin (HbA1c). This process is irreversible and is carried out through a non-enzymatic slow reaction (so-called glycation or glycation).
The rate of glucose binding to hemoglobin depends on the amount of the former, that is, the higher the amount of sugar, the more hemoglobin binds to it and the higher the glycated hemoglobin index.
Due to the fact that the life cycle of red blood cells is only 120 days, this indicator (that is, the degree of glycation) is determined during this period. In other words, the study evaluates “sugar content” over the last 3 months or the average daily glucose level during this period. After 120 days, red blood cells are gradually renewed and the next study will display the amount of blood glucose over the next 3 months.
The indicator is expressed as a percentage (that is, the ratio of glycated hemoglobin to the total content of unchanged protein). However, when assessing the results of the study, it should be taken into account that the binding of glucose and hemoglobin does not occur immediately, and therefore the results of the analysis indicate the average value for 120 days.
Glycated and glycosylated hemoglobin: what is the difference
Various terms are used to refer to the combination of red blood cells and carbohydrates:
- glycosylated;
- glycated;
- glycohemoglobin;
- hba1c.
In fact, all these terms refer to the same compound. But there is a difference between them:
- glycosylated hemoglobin - a connection between glucose and red blood cells through the action of enzymes on them;
- glycated hemoglobin is a connection between glucose and red blood cells without the influence of foreign substances.
The resulting conglomerate becomes indestructible, so it can be easily determined using laboratory tests. Red blood cells combined with sugar will circulate with it for all 120 days. Therefore, the laboratory assistant can determine how long the reaction takes place, and how large concentrations were formed during the interaction of hemoglobin with carbohydrates.
The glycation reaction that occurs in the body is called in vivo. It does not require exposure to any enzymes. Therefore, the determination of the indicator is the most accurate and reliable.
Glycosylated hemoglobin: norm in women by age in the table
Women are characterized by periodic blood renewal. This is related to the menstrual cycle. Some formed elements leave the woman’s body. A change in this indicator is also found in pregnant women, since they develop an additional circle of blood circulation through the placenta and their hormonal levels change. During pregnancy, there is a risk of gestational diabetes mellitus.
The level of the indicator depends on the woman’s age; it is presented in the table.
| Age | Quantity, % |
| Under 39 years old | Less than 5.8 |
| From 40 to 60 years | Less than 6 |
| From 61 years and above | Less than 6.5 |
The older the woman, the higher the ability of red blood cells to combine with sugar. With age, metabolism deteriorates, the effect of insulin, aimed at sending glucose to target cells, decreases. Therefore, the indicators are increasing.
If the indicator number exceeds 6.5%, the doctor will suggest a diagnosis of diabetes mellitus. To confirm it, it is necessary to conduct a series of laboratory tests that will confirm or refute the diagnosis.
Find out more about the normal and abnormalities of glycosylated hemoglobin during pregnancy.
Glycosylated hemoglobin: norm in men by age in the table
Men are characterized by more stable indicators. With age, metabolism slows down only after 50 years. Therefore, an increase in the rate is observed upon reaching this age.
The normal level of the indicator for men is presented in the table below.
| Age | Quantity, % |
| Under 50 years old | Less than 5.9 |
| From 51 to 60 years | Less than 6 |
| From 61 years and above | Less than 6.5 |
The reason for exceeding the indicator is also a slowdown in the release of excess substances through the kidneys. The organ functions worse, so compounds with red blood cells accumulate in the blood. Elderly people, both men and women, are prone to this indicator.
The normal level of glycosylated hemoglobin (hba1c) is defined by the IFCC (International Federation of Clinical Chemistry and Laboratory Medicine).
Evaluation of results
Indicators above the norm (6.5-7.5%) can be detected when there is a threat of diabetes or a lack of iron in the patient’s body. A level above 7.5% of glycated hemoglobin is the norm for diabetes mellitus (that is, it confirms the presence of this pathology).
So, summing up all of the above, the test indicators are interpreted as follows:
- 4.5-6.5 percent is the norm in healthy people;
- 6.9 — presence of SD;
- 7 percent or more is the norm for glycated hemoglobin in type 2 diabetes.
As a rule, the normal level of glycated hemoglobin is higher than the normal fasting glucose level (3.3-5.5 mmol per liter).
This is due to fluctuations in the amount of glucose during the day. For example, immediately after eating, this indicator can reach 7.8, but during the day its normal fluctuations are 3.9-6.9 mmol per liter.
According to research, a normal amount of glycated hemoglobin (about 4%) usually corresponds to an average glucose level of 3.9, and a figure of 6.5% corresponds to a level of 7.2 mmol per liter.
However, in people with the same average amount of glucose, the amount of glycated hemoglobin can vary within 1%. This happens because this indicator can be affected by various pathologies, stress, and deficiency of microelements (most often iron).
Deviations from normal levels of glycated hemoglobin can be observed during pregnancy, due to the development of diabetes mellitus or anemia in pregnant women. Therefore, it is recommended that pregnant women take this test only in the first trimester, due to the fact that cardinal changes occur in the mother’s body in the future and the determination of glycated hemoglobin, which shows the average amount of hemoglobin combined with glucose, can give distorted (false) results.
In children, these indicators should be equal to those in adults, but a slight deviation downward is allowed.
Advantages and disadvantages of analysis
Pros of this study:
- No preparation for the procedure is required.
- The most accurate compared to other tests aimed at identifying diabetes.
- The method is simpler and faster to implement.
- Allows you to monitor treatment and track the dynamics of disease progression.
- The psycho-emotional state of the patient does not affect the result of the analysis.
- Infections will also not change the clinical picture.
Disadvantages of this procedure:
- The cost of testing is higher than other methods of studying glucose levels.
- This test is not suitable for people suffering from hemoglobinopathy and anemia.
- Available only in large clinics. In some regions it is not possible to conduct such a test.
- There may be a falsely elevated result due to thyroid dysfunction.
- Pregnant women should not rely on the indicators of this analysis (false-positive results are too frequent). Otherwise, the woman will be injured during childbirth or lose the child.
First of all, you should understand what the difference is between glycosylated and regular hemoglobin. Glucose slowly interacts with Hb type A so that the result is a compound called glycated hemoglobin, and there are several types of it (a, b, c).
Hb type a1c predominates. It is used in medical practice for diagnostics. The appearance of the analysis is associated with limitations in determining blood glucose levels.
Blood test for glycated hemoglobin: how to prepare
The described analysis should be taken four times a year. This frequency of testing will help monitor changes in glucose levels. Blood should be donated on an empty stomach in the morning. In case of bleeding or blood transfusions, the analysis is postponed for several weeks.
It is recommended that the study be carried out in one laboratory, since different institutions use different methods for determining this indicator. All patients who suspect they have diabetes should undergo this test, since elevated glycated hemoglobin may be present even when they seem to be feeling well. Timely diagnosis allows you to prevent harmful consequences.
How is the determination made?
A blood test for glycated sugar is performed in a specialized clinical diagnostic laboratory. The material for the study is submitted in the morning, preferably on an empty stomach (in comparison with the usual determination of glucose, this condition is not fundamental). Within one working day after taking the test, you can receive the result of the examination. In the case of a blood transfusion, it is better to postpone the analysis of the glycated fraction, since the incoming red blood cells may distort the actual level of this compound.
Advantages of this method
Among other things, this study has several advantages:
- this analysis is the most informative and accurate, as it helps to detect diabetes in the early stages;
- It is recommended to do the analysis on an empty stomach, but sometimes this rule can be neglected;
- the analysis does not take much time and requires minimal costs with maximum accuracy of the result;
- Using this test, the doctor monitors the patient and the effectiveness of therapy.
Disadvantages of the method
- The cost of the test is higher than the usual blood glucose test.
- A decrease in the amount of thyroid hormones can lead to a false increase in HbA1C levels (that is, glucose is not increased).
- If hemoglobinopathy or anemia is present, the test results may be distorted.
- In some cases, when taking high doses of vitamins E or C, falsely low glycated hemoglobin is observed.
- Not all healthcare facilities can carry out this test.
- In some patients, the correlation between average sugar levels and HbA1C is reduced.
Reasons for the increase
An increase in the indicator, as a rule, indicates a long-term increase in blood sugar. But these are not always manifestations of diabetes mellitus. Also changes in carbohydrate metabolism include:
- changes in fasting glucose levels;
- change in tolerance to sugars (glucose).
Glycated hemoglobin (the norm for diabetes mellitus) exceeding 6.5% is regarded as the presence of active diabetes mellitus.
In the case when the indicator changes in the range of 6-6.5%, they speak of a prediabetic state, which is accompanied by an increase in the amount of fasting glucose or impaired tolerance to the latter.
Causes and danger of deviations from the norm
Diagnostic tests for the level of carbohydrates in the blood or glucose compounds with hemoglobin are diagnostic markers used to identify common metabolic failures. But glucose level is a relative indicator that depends on many factors. It can change when eating food and during pregnancy. Its level also depends on the individual ability of the human pancreas to produce insulin, on the level of activity and diet.
The significance of the results obtained makes it possible to determine existing pathologies of internal organs. A general decreased level may indicate liver damage, oncological processes, disorders of the autonomic nervous system, and fermentopathy. The increase is present not only in diabetes mellitus. It is typical in cases of pancreatic pathology, stroke, heart attack, endocrine diseases or pregnancy, and in many other cases.
The reason for changes in the level of modified hemoglobin is the uneven content of daily carbohydrate compounds in the blood. The presence of excess, as well as deficiency, can negatively affect the health of the body due to the presence of compounds that have undergone chemical transformations.
Glycated hemoglobin plays an important role in the diagnosis of diabetes mellitus. Thanks to him, the disease can be detected in the early stages of its development. This makes it possible to start treatment in a timely manner.
The level of this indicator is monitored to assess the effectiveness of the therapy. But few people know what it is.
Reasons for the decline
In cases where glycated hemoglobin is below normal, patients experience persistently low sugar levels, which are often accompanied by characteristic symptoms of hypoglycemia. The most common cause of this condition may be a pancreatic tumor (insulinoma), which produces an increased amount of insulin. In this case, the patient does not have insulin resistance, and due to high insulin levels, the amount of glucose decreases, leading to hypoglycemia.
In addition to the tumor described above, a reduced amount of sugar, which determines a decrease in glycated hemoglobin, may be a consequence of the following pathologies/conditions:
- adrenal insufficiency;
- low-carbohydrate long-term diet;
- excessive prolonged physical activity;
- overdose of glucose-lowering drugs (insulin or tablets);
- genetic rare pathologies (Forbes, von Gierke, Hers diseases, as well as hereditary fructose intolerance).
Fetal hemoglobin and its impact on study results
Fetal is the form of hemoglobin that predominates in newborns during the first weeks of life.
Its difference from adult hemoglobin is its better ability to transport oxygen to tissues. As a result, the concentration of this substance in tissues increases and, accordingly, oxidative processes proceed much faster. This means that the breakdown of complex carbohydrates with the formation of glucose occurs at a faster pace, which helps to increase the level of the latter in the blood, which naturally affects the functioning of the pancreas and its production of insulin, and, as a consequence, the results of the test for glycated hemoglobin.
How to donate blood correctly: preparation for the study
Biological material is collected not only from a vein; it is also possible to take blood from a finger. This is determined by the type of parser that is used to determine the value being sought. A sample of biomaterial can be taken at any time during the day. No specific preparation is required, unlike specific testing to determine the glucose level.
Sometimes experts recommend not making any special physical efforts before the analysis. But the determined indicator is not based on the analysis of momentary content, but on the generalized presence of hemoglobin compounds obtained over a certain period. Therefore, the opposite opinion states that performance is not affected by any overload, be it at the level of emotions or in the form of physical overload efforts.
