HbA1c value: what the blood value means

Many people with diabetes are familiar with this dilemma: the next appointment for blood sugar measurement is coming up, and the radical diet is intended to compensate for the small mistakes in nutrition and possibly lower the blood sugar quickly so that the values ​​appear normal again. This is a big mistake because the long-term blood sugar value, the so-called HbA1c value, is crucial for reasonable blood sugar control. This is important for health because reasonable blood sugar control can reduce the risk of complications from diabetes, such as cardiovascular disease.

HbA1c value – what does that mean?

The HbA1c value indicates the proportion of the “sugared” red blood pigment (haemoglobin) in the total haemoglobin. This stable “sugar haemoglobin”, known in technical terms as “glycosylated haemoglobin”  or “HbA1c”, is produced in everyone, not just in diabetes, and is dependent on the average blood sugar concentration. The higher the blood sugar level over a certain period, the higher the HbA1c value.

With the HbA1c value, the average blood sugar level of the last eight to ten weeks can be determined, regardless of whether the values ​​have risen or fallen sharply. For this reason, the HbA1c value is often referred to as the long-term blood sugar value. As early as 1999, the World Health Organization (WHO) recommended the HbA1c value, blood sugar measurement and glucose tolerance test as essential parameters for assessing the quality of diabetic control. The HbA1c value is, therefore, often referred to as the “gold standard” in diabetes therapy.

 

How is HbA1c measured?

To determine the HbA1c value, the doctor takes a blood sample from the fingertip or a vein in the forearm. The blood sample does not have to be taken on an empty stomach. The HbA1c value is then determined in the laboratory. The HbA1c value is not defined as part of a “normal” check-up or as part of the small or large blood count.

HbA1c: NGSP value and IFCC value

According to the “National Glycohemoglobin Standardization Program” (NGSP) standard method, previously used internationally, the HbA1c values ​​were given in per cent. However, technological advances made more precise measurements possible, which led to a reinterpretation of the previous classification.

To do justice to these results, the specification of the long-term blood glucose levels in millimoles per mole of haemoglobin (mmol/mol Hb) was changed at the suggestion of the “International Federation of Clinical Chemistry and Laboratory Medicine” (IFCC). German laboratories usually continue to give both values. If not, a conversion into the other value is also possible.

 If you want to convert the specified laboratory values ​​from micromoles to percentages, you can use the following formula:

Hba1c in mmol/mol Hb = (Hba1c in percent – 2.15) • 10.929

 

HbA1c – how high should the long-term value be in diabetes?

The HbA1c value shows whether the blood sugar is well adjusted. Because the better the blood sugar is controlled, the lower the HbA1c value.

For younger sufferers, the lower the HbA1c value, the lower the risk of secondary diseases. In older patients over 75 years of age, the connections between long-term blood sugar values ​​and secondary diseases are considered less relevant according to the current therapy guidelines.

In any case, the doctor treating you should make an exact assessment of the values ​​in connection with all influencing factors.

HbA1c-Normalwert

The average HbA1c value in healthy children, adolescents and adults is between 4.4 and 6.5 per cent. In people with diabetes, one goal of treatment is to permanently bring long-term blood sugar to between 6.5 and 7 per cent. Then, the blood sugar is considered normal, i.e. well adjusted.

When is the HbA1c value too high?

Values ​​of over 7.5 per cent mean that long-term blood sugar is too high. The blood sugar is then poorly controlled with known diabetes. In this case, a possible therapy adjustment or a further lifestyle change should be discussed in consultation with the doctor. Illnesses like iron deficiency anaemia or renal insufficiency can also result in elevated HbA1c values. If the cause is unclear, further blood sugar measurements can help determine the cause of the high values.

Persistently high blood sugar levels, reflected in a high HbA1c value, damage large and small blood vessels and nerves. Due to constricted or even blocked vessels ( arteriosclerosis ), the tissue is no longer adequately supplied with nutrients. The most common complications include diabetic foot, nerve damage, damage to the cardiovascular system, eye damage and damage to the kidneys.

 

Too low HbA1c value

HbA1c values ​​below 4.4 per cent are considered too low. In people with diabetes, severely reduced values ​​can indicate hypoglycaemia. People with type 1 diabetes are more likely to have low blood sugar. This should be treated as part of the diabetes therapy. Symptoms of low blood sugar include dizziness, sweating, tremors or tachycardia.

In addition, it is essential to know that various diseases, such as haemolytic anaemia or cirrhosis of the liver, can falsify the HbA1c value into values ​​that are too low. Another disease should, therefore, be ruled out as the cause.

How can the HbA1c value be reduced?

If the HbA1c value in a person with diabetes is permanently too high, various approaches can help to lower long-term blood sugar:

• A healthy and balanced diet can help to lower the HbA1c value, especially if you are overweight with type 2 diabetes. People with type 1 diabetes must pay attention to the ratio of insulin consumed to food.
• Sport and exercise can also lower the HbA1c value. Here, too, people with type 1 diabetes must ensure that the amount of insulin they use is reduced to avoid hypoglycaemia.
• Antidiabetics can help with type 2 diabetes to lower blood sugar in the long term. The most commonly used drug is metformin.
• Therapy with human insulin or insulin analogues can also help to reduce long-term blood sugar levels.

If the HbA1c value is too high or too low, medical advice should always be sought to determine possible causes and select a suitable therapy.

The discovery story of HbA1c

The introduction of the determination of the HbA1c value as a standard method was a decisive advance for the control of effective diabetes therapy. The different haemoglobin variants (HbA1, HbA2 and HbF) were determined in 1955, followed 1958 by the separation and identification of the subtypes of HbA1 (HbA1a, HbA1b and HbA1c).

The fact that in HbA1c, glucose is firmly bound to haemoglobin could only be proven in the 1970s. But as early as 1968, the Tehran paediatrician Dr Samuel Rahbar that an increased concentration of HbA1c is associated with diabetes.

Quantitative detection of HbA1c gained importance when it could be shown that reduced blood glucose levels decreased HbA1c values. The development of new methods of determination and analysis was pushed ahead enormously in the following years, especially since the beginning of the eighties. Today, the HbA1c value can be determined within minutes with modern laboratory methods. This makes it easy to ensure close monitoring of the diabetes patient’s metabolic control.