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HbA1c explained

This page describes what the blood test known as HbA1c is, and how it is useful in monitoring diabetes.

Contents

What is HbA1c?

HbA1c is the main clinic blood test used for monitoring long term blood glucose. Glucose in the blood sticks to haemoglobin in red blood cells, making the substance called ‘glycated haemoglobin’, known as haemoglobin A1c or HbA1c for short.

Red blood cells live for about 8–12 weeks before they are replaced by new ones so the HbA1c test tells you how well your blood glucose has been controlled over the previous 8–12 weeks. The more glucose in your blood, the more HbA1c will be present, so the level reported will be higher.

What does the HbA1c test tell us?

The better your blood glucose control the less chance there is of you developing complications from your diabetes, which could lead to eye, kidney or nerve damage, heart disease or stroke. The HbA1c test tells you whether your blood glucose control has altered in response to changes in your diet, physical activity or medication and makes sure you are on target to keep your risk of complications as low as possible.

How often should my HbA1c be measured?

Blood glucose levels vary throughout the day and from day to day, and so HbA1c should be measured regularly but not too frequently. You will normally be tested every three to six months.

HbA1C results and target

It is important that you agree your own personal target with your diabetes care team, as different people will have different targets, depending on their individual circumstances.

For example, if you have had a lot of problems with low blood glucose levels and have had several hypoglycaemic episodes (‘hypos’), a higher target might be appropriate.

Guidelines will usually recommend a target of around 6.5% (48 mmol/mol)- 7.5% (58 mmol/mol) for most people, depending on the type of diabetes and treatment.

The HbA1C results will be expressed either in millimoles per mol (mmol/mol) or as a percentage (%). Table 1 shows how the results compare:

Table 1: Comparison of HbA1C results

HbA1c (DCCT)

HbA1c (IFCC)

(%)

(mmol/mol)

6.0

42

6.5

48

7.0

53

7.5

59

8.0

64

9.0

75

10.0

86

11.0

97

12.0

108

Old method

New method

Useful resources

For further information see Blood glucose monitoring.

 

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