Testing for normal blood sugar

Part 3: What is HbA1C?

Haemoglobin is a protein in red blood cells which carries oxygen on the blood around the body to where it is needed. Many of the complications of diabetes, such as nephropathy and retinopathy, are caused by haemoglobin being glycosylated, or glycated, by glucose in the blood.

What happens is this: Haemoglobin has a life of about 120 days, then it has to be replaced. For this reason, red blood cells are continually being made. During this process, any glucose that is in the bloodstream is incorporated in with the haemoglobin. It's a bit like icing a cake. The trouble is this glycosylation tends to stop the haemoglobin doing its job properly. And the more glucose there is in the blood at the time red blood cells are made, the worse is the glycosylation.

When when you do a finger prick test to determine your fasting or postprandial blood glucose levels, you are only measuring the level at the time the test is done. By measuring glycosylated (or glycated) haemoglobin, which is also called haemoglobin A1c, Hb1c , HbA1c, or A1C, doctors can identify the average plasma glucose concentration over prolonged periods of time. This monitoring the HbA1c in type-1 diabetic patients may improve treatment.¹

What is a 'normal' HbA1c?

Because everyone has some glucose on their bloodstream, we all have a certain amount of glycosylated haemoglobin. The aim is to get that down to as low a level as possible.

The normal range in a healthy person is about 4%–5.9%.² This is the equivalent of an average blood glucose level over the period between 3.3mmol/l and 6.6mmol/l (60mg/dl and 120mg/dl). That said, if the level is in the high 5%s, a prediabetic condition should be suspected.

HbA1c in diabetics

HbA1c in diabetics will be much higher than in a non-diabetic. The aim then is to get it down by lowering blood glucose levels permanently.

HbA1c tests are usually performed at three-monthly intervals. The HbA1c levels are graded thus:

• Less than 6% is ideal
• Less than 7 % is good
• Over 7 % points to inadequate sugar control.
• Over 8.5 % is very poor control

The usual goal is to get HbA1c lower than 7%, but getting it down below 6% would obviously be much better for your health.

Impact of drugs and diet on HbA1c levels³

The use of any therapy used in treating diabetes is to get excess glucose out of the blood stream. The best way is to prevent getting an excess of glucose in the bloodstream in the first place, but that is not the way doctors think. They are taught to think in terms of treatment rather than prevention, and consequently tend to prescribe drugs.

Diabetes drugs work in different ways and have different effectiveness -- some are better than others. These are tabled below.

As you can see, insulin is much more effective than the 'oral hypoglycaemics' as the drugs you take by mouth are called. But there can be serious consequences if blood levels of insulin are high, so injected insulin is used very much as a last resort.

Nevertheless, if a diabetic is to avoid the complications of diabetes it is ESSENTIAL that blood glucose levels are within the normal range to prevent high levels of glycosylation and subsequent harm.

The best way to do this is with the correct — low-carb diabetes diet.

Diet, if strict enough, can lower HbA1c the most. That is what we will aim for on this Diabetes Diet website.

NOTES

Anaemia: If you are anaemic your HbA1c will read much lower than your actual blood sugars and the resulting HbA1c is not a useful gauge of your actual blood sugar control.

Change of diet: Glycosylated hemoglobin measurement is not appropriate where there has been a change in diet or treatment within the last 6 weeks.

References

1. Larsen ML, Hørder M, Mogensen EF. Effect of long-term monitoring of glycosylated hemoglobin levels in insulin-dependent diabetes mellitus. N Engl J Med 1990; 323: 1021–5.
2. Hemoglobin A1c Test. MedicineNet.com.
3. Nathan DM. Clinical practice. Initial management of glycemia in type 2 diabetes mellitus. N Engl J Med 2002; 347: 1342-9