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HbA1c tests: preventing complications and helping cut ‘hidden’ diabetes


Professor Eric Kilpatrick

Hull Royal Infirmary and Hull York Medical School

The HbA1c test can help reduce the chances of diabetes complications. But it can do far more than that. So what is it and how can it help?

The Haemoglobin A1c (HbA1c) test is key to better diabetes treatment. The blood test indicates the patient’s average blood sugar levels over the previous six to eight weeks, unlike glucose tests which show only current levels.

HbA1c can be used to diagnose diabetes, spot those at risk, monitor treatment, and help prevent complications.

Reducing the chances of complications

Professor Eric Kilpatrick of Hull Royal Infirmary and Hull York Medical School and author of over 50 papers involving HbA1c, says: “Keeping the HbA1c at the target level substantially reduces the likelihood of a patient developing diabetes complications such as eye, kidney, nerve or heart problems. Even in people with
complications, keeping HbA1c at their ideal level reduces the chances of them getting worse.”
Using the test may impact the level of ‘hidden’ diabetes — around 850,000 people have diabetes unknowingly.

Finding the undiagnosed

Prof Kilpatrick, who is also President of the Association for Clinical Biochemistry and Laboratory Medicine, says: “Traditionally, most people with diabetes have been diagnosed by a blood glucose test taken after overnight fasting. Some diabetes experts believe that many people remain undiagnosed partly because it is hard to catch them before breakfast.

“However, the HbA1c test, unlike blood glucose tests, shows the same results whether or not someone has eaten, so it has been recommended that the use of HbA1c be extended to diagnose people as having Type 2 diabetes, not to just monitor existing patients.”

As a result, in the last two years the HbA1c test has been added to blood glucose testing as another diagnosis option for Type 2 diabetes in the UK. Prof Kilpatrick says: “It seems likely that HbA1c testing will become an increasingly popular option.”

Regular testing to improve health

If you are offered a HbA1c test, expect to be asked about your background and state of health. Conditions such as anaemia, kidney disease or an abnormal type of haemoglobin, can affect the result. If HbA1c can be used, a level confirmed to be at or above 48mmol/mol diagnoses someone as having diabetes while 42-47mmol/mol indicates a high risk of developing diabetes in the future.

Patients with diabetes should expect to have HbA1c measured at least annually. Those whose treatment for blood glucose levels is being changed, or whose blood glucose is initially high, may be offered HbA1c testing as often as quarterly.

What is HbA1c and why does it matter? 

The term HbA1c refers to glycated haemoglobin. It develops when haemoglobin, a protein in red blood cells, joins with glucose in the blood, becoming ‘glycated’.

The amount of glucose that combines with haemoglobin is directly proportional to the total amount of sugar that is in your system.

For people with diabetes the higher the HbA1c, the greater the risk of developing diabetes-related complications.

Because red blood cells in the human body survive for eight to twelve weeks before renewal, glycated haemoglobin (HbA1c) tests can reflect average blood glucose levels over that period, providing a longer-term gauge of blood glucose control.

People with Type 2 diabetes who reduce their HbA1c level by 11 mmol/mol are:


19 per cent less likely to get cataracts


16 per cent less likely to suffer heart failure


43 per cent less likely to suffer amputation or death due to peripheral vascular disease.

People with Type 1 diabetes are likely to experience similar benefits if they are able to reduce their HbA1c



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