The HbA1c value (long-term blood sugar value)

Definition - What is the HbA1c value?

The HbA1c value plays an important role in the diagnosis and treatment of diabetes mellitus. Ultimately, it is the normal red blood pigment hemoglobin (HbA), to which, however, glucose is attached. This attachment, chemically known as glycation, takes place spontaneously and depends on the level of blood sugar, i.e. the glucose concentration in the blood. The higher this is, the more hemoglobin is glycated to HbA1c. The HbA1c value thus indicates the proportion of HbA1c in the total hemoglobin. Since the hemoglobin is only broken down after 8-12 weeks, the proportion of HbA1c indicates how high the blood sugar was in the last 2-3 months. The higher this was, the higher the HbA1c value, which is why it is also referred to as “blood sugar memory” or “long-term blood sugar” and is very well suited for follow-up checks in diabetes therapy. It is also becoming increasingly important in the diagnosis of diabetes mellitus.

When is the HbA1c value determined?

HbA1c plays a central role in regulating blood sugar levels in patients with type II diabetes mellitus, as it is a prognostic factor for long-term effects such as vascular and nerve damage. Compared to the normal blood sugar value, the value has the advantage that it is less subject to daily or daily fluctuations and that even short-term fasting of the patient shortly before the check-up does not have a major impact. It is therefore very suitable for monitoring the course of therapy in diabetes mellitus. It is not determined daily, but usually every 3 months, so that the doctor can assess the effects of the therapy and adjust them if necessary. In type II diabetes mellitus, the goal is to keep HbA1c between 6.5% and 7.5% in order to prevent long-term effects as far as possible.

The HbA1c can also be used to diagnose diabetes mellitus: if it is above 6.5%, the diagnosis can be made, if it is above 6.0%, this can additionally support a suspicion that arose, for example, on the basis of typical symptoms. If the value is below 5.7%, diabetes mellitus is very unlikely. However, if the value is between 5.7-6.5%, diabetes mellitus cannot be ruled out and an oral glucose tolerance test (oGTT) must be carried out if the disease is suspected.

You can find more about diagnostics and therapy at Diabetes mellitus

How is the value determined?

HbA1c determination

The doctor determines the HbA1c value by taking a blood sample. For this purpose, venous blood is drawn as standard and the value is determined from this. An alternative to this is now offered by special devices that can also measure the value in capillary blood, for this only a drop of blood has to be taken from the finger, similar to conventional blood sugar determination. However, this technique has not yet established itself in most practices, and determination from venous blood is still the gold standard.

Blood collection

The HbA1c is determined from blood that was usually taken from the patient via the vein. For this, the laboratory needs so-called whole blood, which is sent to the laboratory in an EDTA tube. The measurement of the value is now usually done fully automatically by means of photometry in an enzyme immunoassay (ELISA). Since the values ​​within a sample can fluctuate strongly, measurements are always taken several times and then a mean value is formed that reliably indicates the HbA1c value.

Is there a quick test?

In the meantime, devices have been developed that determine the HbA1c value from the capillary blood of the fingertip, but these are intended for use in the doctor's office.

You can buy “diabetes test strips” in the pharmacy, but these measure the glucose content in the urine and can neither clearly prove nor rule out diabetes mellitus. If an increased value is detected here, a doctor must be consulted in any case, who can then carry out a comprehensive diagnosis.

As a patient, should you also measure the HbA1c value yourself?

Patients with diabetes mellitus should regularly measure their blood sugar and learn to assess the course of their illness themselves; there are special patient training courses for this. Blood sugar can be measured quickly and easily, and there are even automatic measuring devices that the patient can wear on the arm.

Devices can be purchased for the HbA1c measurement, but it is questionable how reliable they are. In addition, a measurement by the patient would not make much sense, since the assessment and possible adjustment of the therapy must be carried out by a doctor. In any case, this will determine the value with a blood sample, which also has the advantage that other values ​​such as blood lipid values ​​can also be determined at the same time. Due to the lack of usefulness, independent measurement is not recommended for diabetics; patients should limit themselves to conventional blood sugar measurement.

Standard values

The HbA1c value is the proportion of glycated hemoglobin in total hemoglobin. It is measured in mmol / mol Hb, but in clinical practice it has become established as a percentage. The normal value is an HbA1c of 4-6%, which means that 4-6% of the total hemoglobin has a glucose residue.

There is also the option of converting HbA1c into a mean blood sugar value, which is usually easier for patients to understand. For example, an HbA1c of 5.0% corresponds to a mean blood sugar of 70 mg / dl.

Costs for determining the HbA1c

The costs for an HbA1c determination are between 12-14 euros, depending on the laboratory. If diabetes mellitus has already been diagnosed, i.e. if the value is determined for monitoring the progress, it can be billed as a health insurance benefit. As part of the preventive medical check-up, the Association of Statutory Health Insurance Physicians for the Early Detection of Diabetes Mellitus stipulates that glucose should be determined in blood and urine from the age of 36. An HbA1c measurement is not part of preventive care and is therefore not billed as a health insurance benefit, but as an individual health service (IGeL), the costs must be borne by the patient himself.

Are there alternatives to the HbA1c value?

An alternative to the HbA1c value is the simple determination of blood sugar. The disadvantage of this value, however, is that it depends on many factors and also fluctuates over the course of the day. A progress assessment would therefore always have to be done soberly and would never be realistic, since the value only shows a snapshot and depends on the behavior of the patient before the measurement, in particular diet and sporting activity. This value can easily be measured at home after appropriate training and can be used as a daily self-control, but the HbA1c is much more suitable for the course and adjustment of therapy.

The HbA1c value can also be used for diagnosis: Diabetes mellitus is diagnosed with a value above 6.5% or below 5.7% is excluded. A good alternative to this is the implementation of an oral glucose tolerance test (oGTT), which has to be carried out anyway if the HbA1c is between 5.7-6.5%. Although this is more complex to carry out, it delivers reliable results.

How can I lower my HbA1c level?

The HbA1c is the most important predictive marker, especially in diabetes mellitus type II, with it and its course the risk of long-term effects of the disease can be estimated. These include primarily

• cardiovascular diseases such as myocardial infarction or CHD

• Strokes

• Nerve damage with diabetic retinopathy or polyneuropathy

• diabetic kidney damage

• diabetic foot syndrome

Therefore setting the HbA1c to values ​​between 6.5 and 7.5% plays a central role in the therapy of every diabetic. In type I diabetes mellitus, this must be done directly by administering insulin, since it has a fundamentally different mechanism of development than that of type II. In the case of type II diabetes mellitus, on the other hand, an attempt is first made to lower HbA1c by changing one's lifestyle. Above all, this includes weight loss, sport and regular exercise as well as a change in diet. Regarding nutrition, it should be noted that under no circumstances have to be foregoing everything and that a balanced, tasty diet can be found with good nutritional advice. In general, diabetics should make sure that a maximum of 30% of the daily nutrients are fats, especially saturated fatty acids should be avoided. It is also important to consume sufficient fiber from whole grain products, legumes or vegetables, for example. Dietary fiber cannot be absorbed in the intestine and thus leads to a feeling of satiety without increasing blood sugar. So-called “diabetic food” is not recommended by the German Diabetes Society DDG, as it often contains a lot of the fruit sugar fructose, which also has a negative effect on HbA1c. You should also be careful with drinks such as soft drinks, juices and energy drinks, whose sugar content is often underestimated.

If this change in lifestyle is implemented consistently, this alone can reduce HbA1c by 1-2 percentage points. Only if this does not have sufficient effect will the doctor initiate drug therapy.

Read more here to Diet in Diabetes

You will also find an overview of everything on the topic here nutrition

What role does HbA1c play in pregnancy?

A complication in pregnancy is pregnancy-induced GDM (Gestational Diabetes Mellitus). This refers to diabetes that appears for the first time during pregnancy and generally disappears again after delivery. The reason for this is the change in hormones during pregnancy.

However, the HbA1c plays a subordinate role here: For screening of GDM, in the 24.-28. During the week of pregnancy, a 50 g glucose challenge test (GCT) or a fasting blood sugar test was performed. Normal blood sugar is also measured during the course, since GDM usually only exists during pregnancy and an exact course does not play a major role. However, if type II diabetes mellitus is suspected or if GDM occurs before the 24th week of pregnancy, the HbA1c value must always be determined.