HbA1c test: what your result means

HbA1c is probably the single most important number on a diabetes report. Unlike a fasting sugar, which tells you about one morning, HbA1c gives a picture of your average sugar over the past two to three months. That is why doctors use it both to diagnose diabetes and to check how well treatment is working.

What does HbA1c actually measure?

Haemoglobin is the protein inside red blood cells that carries oxygen. When sugar is present in the blood, some of it sticks to haemoglobin. The higher your sugar has been, the more haemoglobin gets “sugar-coated”. This coated form is called glycated haemoglobin, or HbA1c.

A red blood cell lives for about three months, so HbA1c reflects roughly that period. The most recent month counts for more than the earlier months. This means a few good or bad days just before the test do not change it much, and you do not need to fast for it.

How do Indian labs report HbA1c?

Most Indian labs print HbA1c as a percentage (for example 7.2%). Some reports also show it in mmol/mol (the international IFCC unit), and many add an estimated average glucose (eAG) in mg/dL. An HbA1c of 7% corresponds to an average glucose of about 154 mg/dL. You can convert your own value with the HbA1c to average glucose converter.

The report will often name the method, such as HPLC or capillary electrophoresis. Good labs use methods certified against international standards (NGSP), so results from different reliable labs should be broadly comparable.

What do the numbers mean?

For diagnosis, the American Diabetes Association uses these HbA1c ranges:

• Below 5.7%: usually normal
• 5.7% to 6.4%: prediabetes, a higher risk of developing diabetes. Read what prediabetes means.
• 6.5% or higher: diabetes, usually confirmed with a second test unless the sugar is clearly very high with symptoms

HbA1c is one of several tests. Fasting sugar and the glucose tolerance test can also diagnose diabetes, and sometimes they disagree. Read normal blood sugar levels for those ranges.

What should my target be if I have diabetes?

Many adults with diabetes aim for an HbA1c below 7%, because this lowers the risk of eye, kidney and nerve damage. But the target is personal. Your doctor may suggest a lower goal if you are young, newly diagnosed and not prone to low sugars. A higher, safer goal is often chosen for older people, people with frequent hypoglycaemia (low sugar), or those with heart disease or other serious illness. Ask your doctor what your own target is and why.

When can HbA1c be misleading?

HbA1c depends on red blood cells living a normal lifespan and on the lab being able to read your haemoglobin correctly. This matters a great deal in India, where anaemia and inherited haemoglobin conditions are common.

• Iron deficiency anaemia tends to push HbA1c up, so the result can look worse than your real sugar control. It can fall once the iron is corrected.
• Recent blood loss, a blood transfusion or haemolysis (red cells breaking down early) tends to push HbA1c down, because the red cells are younger.
• Thalassaemia trait and haemoglobin variants such as HbS, HbE or HbD are common in parts of India. Depending on the variant and the lab method, HbA1c may read falsely high, falsely low, or may not be reportable at all. A good lab will add a comment if it sees an unusual pattern.
• Advanced kidney disease, liver cirrhosis and pregnancy also change red cell turnover, so HbA1c is less reliable.
• Some medicines, such as dapsone, can lower HbA1c by shortening red cell life.

If your HbA1c does not match your glucose readings, tell your doctor. They may check your blood count, ferritin or haemoglobin electrophoresis, and rely more on glucose readings or a continuous glucose monitor (CGM) instead.

How often should HbA1c be checked?

If you have diabetes, HbA1c is usually checked about every three months when treatment is being changed or targets are not met, and at least twice a year when things are stable. If you have prediabetes, doctors usually recheck it at least once a year. Your doctor will tell you what interval suits you.

Can HbA1c come down?

Yes. Changes in food, activity, weight and medicines can lower HbA1c over weeks to months. Because it reflects about three months, it is usually not useful to repeat it after only a few weeks. Some people with type 2 diabetes can even bring HbA1c back below the diabetes range without medicines. Read can diabetes be reversed.

What should I ask my doctor?

• What is my HbA1c target, and why?
• Could anaemia, thalassaemia or kidney problems be affecting my result?
• Does my HbA1c match my sugar readings at home?
• When should I repeat the test?

If your HbA1c is in the diabetes range, or you are unsure what it means for you, book a consultation with an endocrinologist.