Glycated hemoglobin (HbA1c): how to detect prediabetes in time

Contents:

• What is glycated hemoglobin (HbA1c)
• What is the norm of glycated hemoglobin
• Deviations from the norm
• How to lower glycated hemoglobin
• How to properly take a glycated hemoglobin test

Prediabetes often develops unnoticed: a person may have no pronounced complaints, feel relatively normal, and learn about a disorder of carbohydrate metabolism only after laboratory testing. That is why glycated hemoglobin (HbA1c) is considered one of the important indicators for early detection of the risk of type 2 diabetes mellitus. It helps assess not a one-time increase in glucose, but the average blood sugar level over the previous 2–3 months.

Unlike a regular fasting glucose measurement, HbA1c shows a more stable picture: whether there were prolonged periods of elevated glucose levels, how the body regulates carbohydrate metabolism, and whether there are grounds for additional testing. This is especially important for people with excess weight, a hereditary predisposition to diabetes, high blood pressure, a sedentary lifestyle, or changes in other laboratory indicators.

In this article, we explain what HbA1c means, which values are considered normal for different groups of patients, why the indicator may be higher or lower than normal, and how to properly prepare for testing. We will also explain when lifestyle changes are the first priority, and when it is worth consulting a doctor for more detailed diagnostics and risk control.

What is glycated hemoglobin (HbA1c)

Glycated hemoglobin is a form of hemoglobin that forms when glucose from the blood attaches to protein in erythrocytes. Since erythrocytes remain for approximately 120 days, the HbA1c indicator helps assess what the average glucose level was over the past 2–3 months. According to National Institute of Diabetes and Digestive and Kidney Diseases, this test is used to detect prediabetes, diagnose diabetes mellitus, and monitor the course of the disease.

Unlike a regular fasting glucose test, HbA1c does not depend only on what a person ate the day before or on the day of testing. It shows a long-term trend, so it can be informative even when a one-time glucose value is within the normal range. That is why determination of glycated hemoglobin is often recommended for people with risk factors for disorders of carbohydrate metabolism.

The doctors of «Oxford Medical» recommend assessing HbA1c not in isolation, but together with other data. To determine the risk of diabetes, it is important to take into account age, weight, heredity, blood pressure, the presence of concomitant diseases, and the results of other examinations. If the indicator approaches the prediabetes range or already corresponds to it, it is worth consulting a doctor — an endocrinologist will help assess the risks in time and determine further tactics.

What is the norm of glycated hemoglobin

The HbA1c norm for most adults without diabetes is below 5.7%.

The doctors of «Oxford Medical» note: it is important to understand that the level of glycated hemoglobin is not assessed only by the table. It should be taken into account that the result may be affected by anemia, pregnancy, kidney diseases, some disorders of blood formation, and other conditions. Therefore, HbA1c should be assessed together with the fasting glucose level, evaluation of complaints and medical history, and the patient’s general health condition.

Glycated hemoglobin: norm by age

In adults, the standard diagnostic limits of HbA1c usually do not depend on age: below 5.7% is the norm, 5.7–6.4% is prediabetes, 6.5% and higher is possible diabetes. But with age, the doctor evaluates accompanying factors more carefully: cardiovascular diseases, chronic kidney disease, anemia, medication use, and the risk of a sharp decrease in glucose.

In young people, HbA1c approaching the prediabetes threshold is often a signal to reconsider nutrition, physical activity, and weight. At an older age, it is important not only to lower the indicator, but also to do it safely, without episodes of hypoglycemia and deterioration of the general condition. Therefore, the diagnostic limits remain common, but further tactics should be individual.

Glycated hemoglobin: norm in women

For most adult women without pregnancy, HbA1c below 5.7% is considered normal. If the indicator is in the range of 5.7–6.4%, this may indicate prediabetes and requires attention, even if well-being does not change.

Women should monitor carbohydrate metabolism more often if they have excess weight, polycystic ovary syndrome, a history of gestational diabetes, high blood pressure, or cases of type 2 diabetes in the family. In such situations, HbA1c helps identify risks before pronounced symptoms appear.

Glycated hemoglobin: norm in men

In men, the HbA1c norm does not differ from the general diagnostic limits, but the risk of an increased indicator may rise with abdominal obesity, sedentary work, arterial hypertension, lipid metabolism disorders, and chronic stress.

Men often consult a doctor only when noticeable complaints appear: intense thirst, frequent urination, fatigue, visual deterioration, or slow wound healing. Therefore, preventive HbA1c monitoring is useful even without symptoms, especially after the age of 40 or earlier if risk factors are present.

Glycated hemoglobin: norm in children

In children and adolescents, the same HbA1c limits as in adults are used to diagnose prediabetes and diabetes mellitus: below 5.7% is the norm, 5.7–6.4% is prediabetes, 6.5% and higher is possible diabetes. But the result should always be assessed taking into account the child’s age, complaints, body weight, heredity, and data from other examinations.

Testing may be recommended in case of excess weight, hereditary predisposition to diabetes, signs of insulin resistance, increased thirst, frequent urination, rapid fatigue, or unexplained weight loss. If HbA1c is outside the normal range, the doctor may prescribe additional tests, in particular fasting glucose or a glucose tolerance test, to clarify the state of carbohydrate metabolism.

Glycated hemoglobin: norm in pregnant women

During pregnancy, HbA1c has certain features: due to physiological changes in the body, the indicator may be lower than in non-pregnant women. Therefore, HbA1c is not the main test for diagnosing gestational diabetes. For this purpose, blood glucose measurement and an oral glucose tolerance test are used more often.

If a woman already has diabetes mellitus or a disorder of carbohydrate metabolism during pregnancy, HbA1c may be used as an additional monitoring indicator. According to American Diabetes Association Standards of Care in Diabetes, during pregnancy, an HbA1c target below 6% may be optimal if this can be achieved without a significant decrease in glucose.

Glycated hemoglobin: norm for diabetics

For people with already established diabetes mellitus, HbA1c is used not so much for diagnosis as for monitoring the course of the disease. In many adults, a value around or below 7% is considered a target, but this is not a universal norm for everyone. The target value may be lower or higher depending on age, duration of diabetes, risk of hypoglycemia, and the condition of the heart, kidneys, and nervous system.

The doctors of «Oxford Medical» note: the effectiveness of diabetes treatment should not be assessed only by one HbA1c number. For example, the same indicator may have different significance for a young person without complications and for an older patient with cardiovascular diseases. The monitoring plan should be determined by a doctor, and it is important for the patient to undergo regular check-ups, monitor glucose, and not change therapy independently.

Glycated hemoglobin in prediabetes

Prediabetes is a condition in which the glucose level is already higher than normal, but has not yet reached the criteria for diabetes mellitus. For HbA1c, this corresponds to the range of 5.7–6.4%. This exact interval can be described as the glycated hemoglobin level of prediabetes, at which it is worth not waiting for symptoms to appear, but starting preventive changes.

The closer HbA1c is to 6.4%, the higher the risk of prediabetes progressing to type 2 diabetes. According to National Institute of Diabetes and Digestive and Kidney Diseases, within the range of 5.7–6.4%, the risk of diabetes increases together with the increase in HbA1c. At this stage, it is still possible to significantly influence the prognosis: reduce body weight if it is excessive, increase physical activity, improve nutrition, sleep, and blood pressure control.

The doctors of «Oxford Medical» recommend consulting a specialist if the HbA1c result is within the prediabetes range, in order to create a realistic prevention plan and determine how often the examination should be repeated.

Deviations from the norm

A deviation of HbA1c from the norm does not always mean diabetes mellitus, but it requires explanation. The indicator may change not only because of a prolonged increase in glucose levels, but also because of conditions that affect erythrocytes or hemoglobin. According to National Institute of Diabetes and Digestive and Kidney Diseases, the HbA1c result may be inaccurate after blood loss, blood transfusion, with some forms of anemia, kidney diseases, and other conditions due to which erythrocytes renew faster or slower than usual.

To correctly assess the result, the doctor takes into account:

• fasting glucose level;
• the patient’s complaints;
• concomitant diseases;
• medications that the person takes regularly or as a course;
• results of previous examinations;
• complete blood count, kidney and liver function indicators if necessary.

If HbA1c is higher or lower than the expected level, the doctor may recommend a repeat test or additional laboratory tests. This helps understand whether there really is a disorder of carbohydrate metabolism, or whether the result may have changed for other reasons.

Why glycated hemoglobin is elevated

Elevated glycated hemoglobin most often means that over the past months, the blood glucose level regularly exceeded the norm. This may be a sign of prediabetes, type 2 diabetes mellitus, or insufficient control of already diagnosed diabetes.

Main causes of increased HbA1c:

• an excess of fast carbohydrates in the diet;
• low physical activity;
• increased body weight, especially in the abdominal area;
• insulin resistance;
• irregular nutrition;
• chronic stress and sleep disorders;
• hormonal disorders;
• taking certain medications that may affect glucose levels;
• insufficiently effective therapy for already established diabetes.

The doctors of «Oxford Medical» note: if high glycated hemoglobin is combined with thirst, frequent urination, fatigue, blurred vision, slow wound healing, or skin xerosis, it is worth consulting a doctor. Such symptoms do not confirm diabetes by themselves, but together with elevated HbA1c they require additional diagnostics.

A prolonged increase in glucose levels can gradually affect blood vessels, nerve fibers, kidneys, and organs of vision. In people with confirmed diabetes, this increases the risk of cardiovascular complications, including myocardial infarction, as well as kidney damage, impaired sensitivity in the feet, and vision problems. That is why it is important to monitor HbA1c and undergo regular preventive examinations, in particular with an ophthalmologist, to detect such a complication as diabetic retinopathy in time.

According to American Diabetes Association, prediabetes increases the risk of developing type 2 diabetes mellitus and cardiovascular diseases. Therefore, when HbA1c deviates from the norm, it is important not to self-medicate, but to determine the cause of the increase together with a doctor.

Why glycated hemoglobin is below the norm

Reduced HbA1c is less common than elevated HbA1c. It may mean that the average glucose level was lower than expected, or that the test result changed due to certain conditions.

HbA1c may be below the norm in the following cases:

• after significant blood loss;
• after blood transfusion;
• with hemolytic anemia;
• with some liver diseases;
• with kidney failure;
• with frequent episodes of hypoglycemia in people with diabetes.

In patients with diabetes, excessively low HbA1c may indicate frequent decreases in glucose, especially against the background of insulin therapy or glucose-lowering medications. It is important to discuss this with a doctor in order to adjust nutrition, physical activity, or the treatment regimen if necessary.

If HbA1c is below the norm in a person without diabetes, the doctor may recommend checking a complete blood count, fasting glucose level, and liver and kidney indicators. This helps understand whether the result truly reflects glucose metabolism, or whether it is associated with other conditions of the body.

How to lower glycated hemoglobin

HbA1c can only be lowered gradually, since the indicator reflects the average glucose level over several previous months. The main goal is to stabilize glucose metabolism.

If HbA1c is elevated to the level of prediabetes, lifestyle change is often the first step. According to Centers for Disease Control and Prevention, reducing body weight by 5–7% and at least 150 minutes of physical activity per week can significantly reduce the risk of developing type 2 diabetes mellitus.

What helps lower HbA1c:

1. Regular nutrition. It is important to avoid long breaks between meals and overeating in the evening, as this may contribute to fluctuations in glucose levels.
2. Fewer fast carbohydrates. It is worth limiting sweets, sweet drinks, white baked goods, excess French fries, fast food, and products with a high content of added sugar.
3. More fiber. Vegetables, legumes, whole grain products, and unsweetened fruits help raise glucose levels more slowly after meals.
4. A sufficient amount of protein. Fish, poultry, eggs, fermented dairy products without added sugar, legumes, and lean meat help maintain satiety longer.
5. Physical activity. Brisk walking, swimming, cycling, therapeutic exercises, or other activities that correspond to the state of health may be useful.
6. Body weight control. Even moderate weight loss when there is excess weight can improve tissue sensitivity to insulin.
7. Sleep normalization. Chronic lack of sleep can worsen glucose regulation and increase the feeling of hunger.
8. Stress control. Prolonged stress can affect hormonal balance, appetite, and glucose levels.

The doctors of «Oxford Medical» recommend not starting strict diets independently. Too sharp a calorie restriction or complete exclusion of entire food groups often leads to breakdowns and does not provide a stable result. It is better to gradually change eating habits and monitor indicators over time.

If a patient has already been diagnosed with diabetes mellitus, lowering HbA1c depends not only on nutrition and activity, but also on correctly selected therapy. You must not independently change medication dosages, stop medicines, or add new agents without consulting a doctor. This can lead both to an increase in glucose and to dangerous hypoglycemia.

How to properly take a glycated hemoglobin test

An HbA1c test does not require special preparation. It can be taken at any time of day, regardless of food intake, because the indicator reflects the average glucose level over the past 2–3 months, not the sugar level specifically on the day of testing.

Before the examination, it is worth taking several points into account:

• if fasting glucose, a lipid profile, or other indicators are prescribed together with HbA1c, the doctor may recommend coming in the morning while fasting;
• it is worth informing the doctor about anemia, recent blood loss, blood transfusion, pregnancy, kidney or liver diseases;
• if the HbA1c result does not match other glucose indicators, the doctor may prescribe a repeat test or additional tests.

Usually, blood for the test is taken from a vein or from a finger, depending on the method. For patients with prediabetes or diabetes, the doctor determines the frequency of HbA1c monitoring individually.

Glycated hemoglobin HbA1c helps detect prediabetes in time and monitor the course of an already diagnosed disease. If HbA1c is elevated, it is important not to postpone a doctor’s consultation. At the stage of prediabetes, dietary changes, physical activity, weight control, and regular monitoring can help reduce the risk of developing type 2 diabetes mellitus. If diabetes has already been established, the HbA1c indicator helps assess how effectively the disease is controlled.

The information in the article is provided for informational purposes and is not an instruction for self-diagnosis and treatment. If symptoms of the disease appear, you should consult a doctor.

Sources:

National Institute of Diabetes and Digestive and Kidney Diseases

American Diabetes Association

Centers for Disease Control and Prevention