HbA1c normal range

What HbA1c measures

HbA1c, also called A1c or glycated hemoglobin, shows your average blood sugar over the past two to three months. Sugar in the blood sticks to hemoglobin inside red cells, and because red cells live about three months, the test gives a longer view than a single glucose reading. You do not need to fast for it. Labs in the US and India often report HbA1c in %, while the UK and many other countries use mmol/mol. Some reports also show an estimated average glucose (eAG) calculated from the HbA1c.

How it compares with fasting glucose

Fasting glucose is a snapshot of your blood sugar after at least 8 hours without food. Under 100 mg/dL (5.6 mmol/L) is normal, 100 to 125 mg/dL (5.6 to 6.9 mmol/L) is the prediabetes range, and 126 mg/dL (7.0 mmol/L) or higher on two tests is in the diabetes range. HbA1c and fasting glucose usually agree, but not always. When they disagree, doctors often repeat the test that was abnormal or add an oral glucose tolerance test. To convert glucose, divide mg/dL by 18 to get mmol/L.

When HbA1c can be misleading

Because HbA1c depends on red blood cells, anything that changes their lifespan can make it read too high or too low. This matters in South Asia, where iron deficiency and hemoglobin variants are common. In these cases, doctors may rely more on glucose tests. If your HbA1c does not match your glucose readings or your symptoms, tell your doctor, as a fructosamine test or a glucose tolerance test may give a truer picture.

• Iron deficiency anaemia can push HbA1c up
• Recent blood loss, a blood transfusion or hemolysis can push it down
• Thalassaemia trait, sickle cell trait and other hemoglobin variants
• Advanced kidney disease and pregnancy

What usually happens next

If your HbA1c is in the prediabetes range, your doctor may suggest lifestyle changes and a repeat test every year or so. Large studies show that losing about 5 to 7% of body weight and being active for about 150 minutes a week lowers the chance of developing type 2 diabetes. If your result is in the diabetes range, your doctor will usually confirm it, then check kidney function, cholesterol, blood pressure, eyes and feet. For many adults with diabetes, the ADA suggests an HbA1c target below 7%, but your doctor will set a personal target.

Questions to ask your doctor

• Is my HbA1c in the normal, prediabetes or diabetes range?
• Do I need a repeat test or a glucose tolerance test to confirm it?
• Could anaemia or a hemoglobin variant be affecting my result?
• What HbA1c target is right for me?
• How often should I have my HbA1c checked?