Dr Maxwell Adeyemi

People with diabetes used to depend on daily finger pricks to measure their blood sugar levels. These tests are accurate, but only in the moment. They are actually very limited as an overall measurement of blood sugar control.

This is because your blood sugar can vary wildly depending on the time of day, your activity levels, and even hormonal changes. Some people may have high blood sugar at 3 am and be totally unaware of it. The A1C test measures the amount of haemoglobin in the blood that has glucose attached to it. The test is used to monitor blood sugar levels, as well as for diagnosis and screening of pre-diabetes and diabetes.

Haemoglobin A1C tests became available in the 1980s and quickly became an important tool in monitoring diabetes control. Haemoglobin A1C tests measure average blood glucose over the past two to three months, so even if you have a high fasting blood sugar, your overall blood sugar may be normal, or vice versa. A normal fasting blood sugar may not eliminate the possibility of type 2 diabetes.

This is why haemoglobin A1C tests are now being used for the diagnosis and screening of pre-diabetes and diabetes. Because it does not require fasting, the test can be given at any time as part of an overall blood screening.

A1C test measure measures the amount of haemoglobin in the blood that has glucose attached to it. Haemoglobin is a protein found inside red blood cells that carries oxygen to the body. Haemoglobin cells are constantly dying and regenerating. Their lifespan is approximately three months. Glucose attaches (glycates) to haemoglobin, so the record of how much glucose is attached to your haemoglobin also lasts for about three months. If there's too much glucose attached to the haemoglobin cells, you will have a high A1C. If the amount of glucose is normal, your A1C will be normal.

Haemoglobin A1C levels

Someone without diabetes will have about five per cent of their haemoglobin glycated. A normal A1C level is 5.6 per cent or below. A level of 5.7 to 6.4 per cent indicates pre-diabetes. People with diabetes have an A1C level of 6.5 per cent or above. There is a calculator that shows how A1C levels correlate to glucose levels. To monitor overall glucose control, people with diabetes should have an A1C test at least twice a year.

More frequent measurements like every three months should be taken if:

· you have type 1 diabetes

· your treatment is being adjusted

· you and your doctor are setting certain blood sugar targets

· you are pregnant

How an A1C test works

The test is effective because of the lifespan of the haemoglobin cells. If your blood glucose was high last week or last month, but it's normal now, your haemoglobin will carry a 'record' of last week's high blood glucose in the form of more A1C in your blood. The glucose that was attached to the haemoglobin during the past three months will still be recorded