An HbA1ca test is blood test which indicates how much of the oxygen carrying red pigment in red blood cells is affected by glucose. The result is usually expressed as a percentage. An HbA1c below 6.5% indicates good glucose control over the previous 8 to 12 weeks. A high value of around 10% would mean that on average the blood levels have been high over the previous 2 to 3 months.
A blood glucose level shows the level of glucose at a particular time, for example, before breakfast. The HbA1c gives a measure of glucose control over a much longer time period-two or three months. This is useful because, of course, blood results can vary enormously over the day and what is important is that, on average, the levels are not too high. HbA1c test levels show a strong correlation with complications of diabetes so that patients with values less than 6.5% have a much reduced risk of complications compared to those with high values.
For most people with diabetes, NICE recommends an HbA1c normal range to be below 6.5%. However targets do need to be individualised for the particular person bearing in mind the risk of hypoglycaemia, quality of life and any other factors such as co-existing medical conditions. In all cases, the patients’ views must be taken into account and the risks of high blood glucose levels balanced by the risks of the treatment.
Dr Steve Hyer
