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HbA1c – What is it?

In our bloodstream we have red blood cells that is made of of a molecule called haemoglobin, glucose sticks to haemoglobin. Glucose sticks to the haemoglobin to make a ‘glycosylated haemoglobin’ molecule, called haemoglobin A1C or HbA1C. The more glucose in the blood, the more haemoglobin A1C or HbA1C will be present in the blood.

Red cells live for 8 -12 weeks before they are replaced. By measuring the HbA1C it can tell you how high your blood glucose has been on average over the last 8-12 weeks. A normal non-diabetic HbA1C is 3.5-5.5%. In diabetes about 6.5% is good.

The HbA1C test is currently one of the best ways to check diabetes is under control; it is the blood test that gets sent to the laboratory, and it is done on the spot in some hospital clinics. Remember, the HbA1C is not the same as the glucose level.

Coincidentally the glucose/HbA1C numbers for good control are rather similar though in the UK and Europe: glucose levels averaging 6.5 mmols/l before meals is equivalent to 7% HbA1C (glucose levels are higher after meals.

HbA1c levels by coincidence nearly equate to glucose levels. So an HbA1c level of 10% means the average glucose level for the previous 10 weeks was 13mmol/l.

But at lower levels there is even less difference, so an  HbA1c of 7% means the average glucose level was 8mmols/l.

HbA1c %
Average blood glucose level mmol/l
13 18
12 17
11 15
10 13
9 12
8 10
7 8
6 7
5 5

The way we will be given our HbA1c readings is changing this year, instead of a percentage figure it will be millimoles per mol. There is no change but you need to know what your target is, here is a conversion chart:

Current HbA1c   (%) New HbA1c (mmol/mol)
6.0 42
7.0 53
8.0 64
9.0 75
10.0 86

Current HbA1c targets of 6.5% and 7.5% are 48 mmol/mol and 59 mmol/mol in the new units.