Synonyms: A1C, HbA1c
Related tests: Blood glucose, Fructosamine, Insulin, Glucagon.
Clinical significance
Glycated haemoglobin makes up about 2% of the haemoglobin in red blood cells and is the result of the non-enzymatic binding of glucose to the haemoglobin molecule. This process occurs in proportion to the average concentration of glucose in the blood throughout the life of the red blood cell (120 days on average). Glycated haemoglobin therefore reflects average blood glucose levels over the last 8-12 weeks.
People with diabetes who have high glucose concentrations have glycated haemoglobin levels 2 to 3 times higher than a person with normal blood glucose.
Clinical indications
Checking the effectiveness of treatment; screening for diabetes mellitus
Sample type
The patient must have a blood sample taken.
Preparation
You must fast for at least 8 hours; a small amount of water is allowed. You must have been standing or sitting upright for at least 30 minutes.
Notes
Recent recommendations from the American Diabetes Association (ADA) support using this test to diagnose diabetes, with 6.5% HbA1c as the decision level.
Haemolytic anaemia or bleeding can falsely lower measured glycated haemoglobin levels, while inherited haemoglobin variants (HbS, HbC) can cause falsely high results.