Haemoglobin A1c (HbA1c)
The HbA1c test measures the proportion of haemoglobin in your red blood cells that has sugar attached to it. Because red cells live for about three months, the result reflects your average blood sugar over the previous two to three months rather than at a single moment. It does not require fasting and can be done at any time of day.
At YGOPH, doctors use HbA1c to diagnose diabetes in adults, to follow children and adolescents living with type 1 diabetes, and to check blood sugar control in women with diabetes who are planning a pregnancy. Good control before conception reduces the risk of miscarriage and birth defects, so the test is an important part of preconception care.
What does HbA1c measure?
Glucose in the blood attaches slowly and permanently to haemoglobin: the more sugar there is in the blood, the more HbA1c forms. The result is given as a percentage (%) or in millimoles per mole (mmol/mol). In adults, a result below 5.7% (39 mmol/mol) is usually considered normal, 5.7% to 6.4% suggests prediabetes, and 6.5% (48 mmol/mol) or more, confirmed by a second test, indicates diabetes.
- Diagnosis of type 2 diabetes in adults with risk factors or symptoms
- Regular follow-up of people with diabetes, usually every three to six months
- Children and adolescents with type 1 diabetes
- Women with diabetes who are planning a pregnancy
- Long-term follow-up of women who had gestational diabetes
Good to know
Using HbA1c to follow diabetes
For many adults with diabetes, doctors aim for an HbA1c of around 7% (53 mmol/mol) or lower, but the target is individual and depends on age, other illnesses and the risk of low blood sugar. Checking HbA1c every three to six months shows whether treatment, diet and physical activity are working.
When HbA1c can be misleading
Anything that changes the lifespan of red blood cells can affect the result. Sickle cell disease and other haemoglobin variants, anaemia, recent malaria, blood loss or a recent transfusion can make HbA1c falsely low or high. It is also not used to diagnose gestational diabetes, because red cells are renewed faster in pregnancy; the oral glucose tolerance test is used instead.
HbA1c and blood glucose tests
HbA1c complements, but does not replace, finger-prick and laboratory glucose tests. Daily glucose checks show variations from hour to hour and help adjust insulin, while HbA1c shows the overall trend. Your doctor will use both, together with your symptoms and any episodes of low blood sugar, to guide your treatment.