HbA1c Blood Test.

What is the HbA1c Blood Test?

The HbA1c (or HbA1) test gives a longer term view of blood sugar (blood glucose) levels. It requires a full blood sample rather than just a single drop of blood, the blood is analysed in a lab so it will take some time to get the results.

The test is made on the Haemoglobin in the red blood cells which retain a 'memory' of the average sugar levels in the blood over the last two to three months (this is the lifetime of the average red blood cell). Where Diabetes is diagnosed this test also gives an indication of the severity of the problem.

The delay involved in sending samples off to the lab may change in the future as an immediate test is now available and used in some areas of the US. Bayer Diagnostics, external link.

It may be to costly (or inaccurate) for the NHS at the moment. Single test products are available in the US for $25 or so (plus shipping).

As well as being used in the original diagnosis, the HbA1c test is used to monitor how well blood sugar levels are being controlled at the regular check-ups following a positive diagnosis. Because the test gives a 3 month or so average measurement it gives a very good idea of how well diabetes is being controlled.

If you are subject to high peaks and very low blood sugar levels the HbA1c test may be misleading as it is an average. Both high peaks hyperglycemia and low dips hypoglycemia can cause problems for diabetic's.

Note: Usually only diabetics who take drugs that encourage the production of insulin or diabetics who directly inject insulin will get low blood sugar levels (hypoglycemia).

HbA1c Target Levels.

National Institute for Clinical Excellence (NICE) guidelinesHbA1c: 7.0% or less
Joint British Societies Guidelines*HbA1c:6.5% or less
Non Diabetic RangeHbA1c: 5.6% or less

* See Diabetes UK: Heart of the Matter page, 21st December 2005. I think it likely the NICE guidelines will be lowered to this shortly.

Targets for individuals will however vary depending on circumstances and may be higher or lower than the above targets.

Younger diabetic's both Type 1's and Type 2's, should generally aim for tighter targets as complication are progressive and more likely to develop the longer you live with diabetes.

Diabetic's who are subject to very low blood sugar levels may be an exception (usually those on insulin or high doses of drugs). With the risks of very low blood sugar hypoglycemia sometimes outweighing the risks of complications.

Generally though even if you cannot achieve these levels, it is worth while aiming to reduce levels towards this as even slightly lower peak blood sugar levels reduce the risks of diabetic complications.

HbA1c to average Blood Glucose
Pop-up Converter

Whole Blood and Blood Plasma.

The pop-up converter above shows both whole blood glucose levels and blood plasma glucose levels. Blood plasma figures are about 12% higher than the equivalent whole blood figures.

More modern meters tend to use whole blood, if in doubt check the meter. Plasma is the clear liquid left after the blood cells are removed from whole blood.

External Links.