Why test your glycated hemoglobin (HbA1c)?

What is HbA1c glycated hemoglobin?

Glycated hemoglobin is noted as HbA1c, on prescriptions or laboratory results:

– “Hb” is hemoglobin,

– “A1c” is the type of hemoglobin analyzed in the assessment.

The glycated form of the hemoglobin molecule

Thus, the biological value of glycated hemoglobin is the binding between hemoglobin and glucose. Therefore, the term “glycated” comes from glucose.

In addition, this binding is proportional to the amount of glucose in the blood. Thus, it is used to determine the concentration of glucose in the blood. In other words, the sweeter the blood, the sweeter the red blood cell is. And as a result, glycated hemoglobin is high, when in a non-diabetic person, the glucose level is mostly low.

What is the lifetime of HbA1c?

HbA1C measures the presence of glucose over the last three to four months. This period of a few months is equivalent to the lifetime of hemoglobin. Indeed, the red blood cells containing hemoglobin are constantly renewed.  They live for about 120 days, then the spleen destroys them.

Why monitor glycated hemoglobin levels when you have diabetes?

First, it is a reference parameter in the balancing of diabetes. Like a black box, HbA1c records all changes in blood glucose levels. It reflects the average blood sugar level.

Therefore, these dosages have 3 objectives:

– Have a global view of the patient’s glycemic control.

– Evaluate and adapt diabetes treatment (insulin, oral anti-diabetic drugs, physical activity, diet).

– Determine the risks of diabetes complications in the short and long term.

Comply with HbA1c objectives to avoid diabetes complications

First, frequent periods of hyperglycemia in the 120 days prior to dosing results in an increase in the value of HbA1c. This decreases when the blood sugar level is properly balanced. Thus, the more regularly a diabetic patient measures his or her blood sugar levels, the better he or she can control it to achieve the goal set by his or her caregivers. Therefore, glycated hemoglobin remains low. Indeed, a low HbA1c avoids the risk of developing complications and hospitalizations related to diabetes.

What is the difference between HbA1c and blood sugar?

Above all, it is important to understand the difference between HbA1c and blood sugar. The first is the average measurement  of blood glucose over a period of 120 days, while the second, with capillary and fasting blood glucose measurements, is a snapshot of the blood glucose at that moment.

First, a blood sample is taken in an analytical laboratory to measure glycated hemoglobin.

How to perform an HbA1c test?

Then, HbA1 is usually measured at least twice a year, to ensure regular monitoring of diabetes control.

Note that the measurement can be done at any time of the day. It is not necessary to fast. Thus, the proximity of a food intake does not influence the HbA1c level.

Finally, the HbA1c rate is expressed as a percentage. Therefore, this figure represents the percentage of hemoglobin in the red blood cell that fixes sugar. For example, its normal value is between 4% and 6% of total hemoglobin.

What is the purpose of a good glycated hemoglobin?

The health care team individually sets the patient’s HbA1C objective. Thus, several parameters are taken into consideration:

– The type of diabetes

– The age of the patient (elderly people considered “fragile” generally have a target of less than 8%)

-The type of treatment

– Complications or non-existent complications

For indication, the High Authority for Health has issued recommendations on the target objectives of HbA1c, depending on the patient’s profile:

– type 2 diabetes, for most cases: less than 7%.

– type 1 diabetes: between 7% and 7.5%.

For information, the HAS has published a table of correspondence between HbA1c and blood glucose levels:

HbA1c targetAverage blood glucose levels before meals (g/L)Average blood glucose levels after meals (g/L)Average blood glucose levels (g/L)
< 6 %< 1< 1,401,26
7 %< 1,20-1,30< 1,801,54
8 %< 1,60< 2,101,82
9 %< 1,80< 2,402,11

Note that the definition of type 2 diabetes is based on the fasting blood glucose measurement. However, several international research institutions tend to modify this definition by replacing it with a glycosylated hemoglobin level of more than 6.5%.

If the HbA1c test results are too high, it is likely that the diabetic patient will not be able to balance his diabetes, that an incident has disrupted him (flu, stress…) or that the treatment is not appropriate.

Therefore, the health care team can adapt the treatment (strengthening of hygieno-dietary measures, adaptation of drug treatment, etc.), depending on the achievement of these objectives.

How to lower glycated hemoglobin?

First, it is important to remember that lowering the HbA1c level takes time. However, this delay depends on the blood sugar level at the beginning of the disease and lifestyle habits.

Therefore, the essential factors to be controlled to maintain the glycated haemoglobin objective set by the diabetologist are:

– The daily intake of the treatment prescribed by his or her attending physician or diabetologist

– Controlling carbohydrate consumption through a balanced diet

– Blood glucose testing several times a day, before and after meals. For example, the use of a connected measuring device, or the addition of the GLUCONEXT connector, allows these measurements to be recorded.

– Regular physical activity is essential. During exercise, the muscles burn the carbohydrates in the body. A walk every day for half an hour is a minimum.

Therefore, these habits are part of your daily routine.

Why is glycated hemoglobin important?

Patients may not be aware that they have poorly controlled diabetes. Indeed, diabetes is devious. As a result, problems can occur without the patient anticipating them. It is therefore essential for the patient to maintain his HbA1c level at a correct level whatever his or her feelings, to protect his or her future health.


 International Expert Committee, « International expert committee report on the role of the A1c assay in the diagnosis of diabetes » [archive] Diabetes Care 2009;32:1327-34