What does the test tell you?
The amount of Haemoglobin that have Glucose molecules permanently attached to them gives an indication of the average blood Glucose level over the previous few weeks; if your Diabetes has not been well controlled and blood Glucose levels have been higher than normal for extended periods of time, then this will be reflected in a high HbA1c result.
Red blood cells are continually being replaced in the body; old ones are broken down and new ones are made in the bone marrow; the average lifetime of a red blood cell is about 120 days; this means that Haemoglobin has approximately 120 days to collect Glucose molecules on it, before it is destroyed and replaced with new Haemoglobin.
The results of the test are either given as a percentage, or as millimoles/mol (mmol/mol); this is the measurement of Haemoglobin that has been glycated; people who do not have Diabetes generally have an HbA1c level of less than 6% (42 mmol/mol); this means that less than 6% of their Haemoglobin molecules have Glucose permanently attached.
The HbA1c level in people who have Diabetes gives a good indication of how well their blood Glucose has been controlled during the previous (2 to 3) months.
Why do I need to have an HbA1c blood test?
Daily blood Glucose tests only provide you with a snapshot of glycaemic control at the moment that you test; the HbA1c test, on the other hand, gives you the big picture by showing how your blood Glucose control has been over the previous couple of months and is useful for you, your doctor and your Diabetic team when assessing your Diabetes and treatment.
Over a longer period of time, consecutive HbA1c tests will provide an overall trend in your Diabetes control; if your HbA1c is progressively rising each time you visit the clinic then it may suggest that your treatment plan needs modifying; if you have Type 2 Diabetes, then perhaps you need to start taking tablets, or Insulin, or start extra treatment.
If your HbA1c level comes as something of a surprise, or if it is particularly high, then you may benefit from doing more frequent blood Glucose testing; this should help to show you, your doctor and Diabetic team where improvements could be made to your treatment plan; the test may also help to motivate you; if your levels are progressively increasing then you may be alerted to the fact that you have been letting your control slip recently; however, if your levels are slowly improving then you should give yourself a pat on the back!
So what HbA1c level should I be aiming for?
There are no hard and fast answers to this question; your target HbA1c or glycated Haemoglobin level will depend on a number of factors and can be different from person to person, you should discuss this with your doctor and Diabetic team; it will also depend on the reference range supplied by the laboratory that performs the test.
As a Very General HbA1c level Guide:
HbA1c levels of less than 6.5% (48 mmol/mol) indicate good control.
HbA1c levels of more than 8.5% (69 mmol/mol) indicate poor control.
Ideal Blood Glucose levels, when self-testing with a blood glucose meter, are:
Adults with Type 1 Diabetes: (4 to 7)mmol/l before meals and no more than 9mmol/l by 2 hours after meals.
Adults with Type 2 Diabetes: (4 to 7)mmol/l before meals and no more than 8.5mmol/l by 2 hours after meals.
During Pregnancy: (3.5 to 5.9)mmol/l before meals and no more than 7.8mmol/l by 1 hour after meals.
Children (under 16) with Type 1 Diabetes: (4 to 8)mmol/l before meals and no more than 10mmol/l by 2 hours after meals.
Children (under 16) with Type 2 Diabetes: This needs to be agreed with your diabetes healthcare team.
The Fructosamine Test:
This test gives an indication of blood Glucose control over the previous (2 to 3) weeks; it is based on the same principle as the glycated Haemoglobin test, but Plasma Proteins with Glucose attached are measured, as opposed to Haemoglobin; some people refer to Fructosamine as GSP or Glycated Serum Protein; the amount of Glucose that attaches itself to the plasma proteins to form Fructosamine depends on the level of Glucose in the blood and the length of time that it is at that level; because plasma proteins have a shorter lifespan, compared to Haemoglobin in red blood cells, Fructosamine gives an indication of blood Glucose control over a much shorter period of time.
Fructosamine levels are useful in the short-term, for example, in assessing the effects of changing a treatment plan during pregnancy, when treatment needs can change drastically and good control is vital; target Fructosamine levels are generally less than 300 umol/l.
Diabetes Related Information Leaflets