Understanding Haemoglobin A-1C (HB A1C)

3D Diabetes Stop Crossword textDiabetes mellitus is a common clinical condition that forms a risk factor for the development of heart disease and stroke. If you suffer from diabetes and have been on treatment for a while, you may undergo regular blood tests to determine how well your blood sugar levels have been controlled with treatment.

The common tests that are performed include fasting blood sugar, post prandial blood sugar (i.e blood sugar test 2 hours after a meal) and heaemoglobin A1c (HbA1c). In this article, we briefly cover HbA1c.

What is HbA1c?

HbA1c, which stands for haemoglobin A1c, is also called glycosylated hemoglobin. Hemoglobin is a component of blood that carries oxygen and gives it a red colour. There are different kinds of hemoglobin in the blood, and HbA1c is one type of it.

Within the blood stream is present glucose. Glucose can attach to hemoglobin in red blood cells, and this hemoglobin is called HbA1c. The average lifespan of a red blood cell is 120 days, following which it dies and is replaced by new blood cells. What this means is that if glucose is attached to these cells, it has been attached to it for 120 days or less.

By measuring the HbA1c, it is possible to determine the control of glucose levels in the blood for 120 days (i.e. 3 months), giving the doctor and patient a good idea as to how well their diabetes is controlled.

What is the normal HbA1c level?

HbA1c is expressed in percentage. The normal value lies between 4% to 6% in patients who are healthy and do not suffer from diabetes. In other words, in healthy individuals, between 4 to 6 out of 100 red blood cells will have glucose attached to it. Below are the values of HbA1c that are seen in clinical practice

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  • Normal (in healthy individuals) = 4 – 6%
  • Normal (in diabetic patients) = 6.1 – 7%
  • High = 7.1 – 8%
  • Very high = 8.1 – 9%
  • Unacceptably high >9.1%


The recommended levels of HbA1c in patients with diabetes that indicates good control of blood glucose levels is below 7%. While this may be hard to attain, a value below 7.5% may be acceptable.

What does a high HbA1c mean?

A high level of HbA1c indicates that the blood sugar has not been very well controlled for the last 3 months or less than that. This may be due to a number of different reasons –

  • Insufficient medication to treat diabetes
  • Poor compliance to medical treatment
  • Taking treatment and continuing with high sugar diet
  • Long standing infections that have not been treated
  • Long term steroid use


Having a high blood sugar over a long period of time can affect the heart, kidneys, eyes and nerves, causing irreversible damage.

For more information on diabetes and heart disease, check out our free patient booklets here.

Dr Vivek Baliga
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