HbA1c Test Normal Range: What Your Result Means

What does the HbA1c test measure?

Haemoglobin is the protein in red blood cells that carries oxygen. Glucose in the blood sticks to haemoglobin, and the higher your blood sugar has been, the more haemoglobin becomes "glycated". HbA1c is the percentage of haemoglobin that carries glucose.

Because red blood cells live for a few months, HbA1c gives a picture of your average blood sugar over roughly the past two to three months. A single heavy meal, a festival sweet or a stressful morning will not change it much. That is why it is useful both for finding diabetes and for checking how well diabetes has been controlled over time.

HbA1c normal range and diagnostic cut-offs

For adults who are not pregnant, NIDDK uses the following thresholds. The same table shows the matching values for other common sugar tests:

Two points are important. First, one abnormal result is usually not enough: NIDDK notes that doctors normally repeat a test, or use a second type of test, to confirm diabetes. Second, these cut-offs are for diagnosis. If you already have diabetes, your doctor will set a personal HbA1c target, which depends on your age, other illnesses and risk of low sugar episodes.

What "prediabetes" means

A result in the prediabetes range means your blood sugar is higher than normal but not high enough to be called diabetes. It is a warning sign rather than a disease label. Many people in this range can lower their risk of developing type 2 diabetes with steady changes to diet, physical activity and weight, under medical guidance. Our clinic has a physician and a dietitian who can advise you on next steps and how often to retest.

HbA1c compared with other sugar tests

• Fasting blood sugar shows glucose at one point in time after at least 8 hours without food. It needs preparation; see our guide on how to prepare for a fasting blood test.
• Oral glucose tolerance test measures how your body handles a measured sugar drink over two to three hours. It is used to diagnose diabetes in pregnancy and sometimes to confirm prediabetes or type 2 diabetes.
• Random blood sugar can be done at any time and is often the first test when someone has symptoms such as heavy thirst or frequent urination.
• HbA1c needs no fasting and reflects the longer-term average, but it can be affected by conditions of the blood, as described below.

Because each test measures something different, it is common for a doctor to order two of them together. The sugar tests available at our centre are listed in the tests catalogue under Diabetes / Sugar Tests.

When the HbA1c result can be inaccurate

HbA1c depends on red blood cells, so anything that changes their life span or the type of haemoglobin can affect it. MedlinePlus and NIDDK list:

• Anaemia and other disorders of red blood cells
• Certain haemoglobin variants (inherited differences in haemoglobin)
• Kidney failure and liver disease
• Pregnancy, especially the second and third trimesters; HbA1c is not used to diagnose diabetes in pregnancy
• Some medicines, such as opioids and certain HIV medicines

If your HbA1c does not match your glucose readings, or you have any of the conditions above, tell your doctor. Glucose-based tests may give a more reliable picture for you. A CBC test, which checks haemoglobin, is sometimes requested alongside to look for anaemia. Thyroid problems can also cause tiredness and weight change; see our guide to the thyroid test normal range.

How often should HbA1c be checked?

For people with diabetes, MedlinePlus advises testing at least twice a year, and more often when treatment is being changed or the target has not been reached. For people without diabetes, how often to screen depends on age, weight, family history and other risk factors; ask your doctor.