HbA1c (glycated haemoglobin): what your result shows and what comes next

What does HbA1c measure?

Haemoglobin is the protein in red blood cells that carries oxygen. When sugar (glucose) circulates in the blood, some of it sticks to haemoglobin and stays there for as long as the red blood cell lives, about three months. The test measures what percentage of your haemoglobin has sugar attached to it.

That is its advantage. A morning blood sugar test shows the sugar in your blood at a single moment, and the value can shift after a late dinner or a bad night. HbA1c shows the average over several weeks, so one day doesn't throw it off.

You don't need to fast for HbA1c, but many labs take the sample in the morning, together with other tests that do require fasting.

What does your HbA1c value mean, by range?

The thresholds above are the ones used by MedlinePlus and the American Diabetes Association. Some labs also report the result in mmol/mol. As a guide, 5.7% is about 39 mmol/mol and 6.5% is 48 mmol/mol.

A single result of 6.5% or more doesn't make a diagnosis on its own. Your doctor will usually ask for a second test, either another HbA1c or a fasting glucose or glucose tolerance test.

What is prediabetes?

Prediabetes means your blood sugar is higher than normal, but not yet high enough to be diabetes. Many people with prediabetes have no symptoms and find out from tests done for something else.

It's a useful warning, because this is the stage where changing your habits has the biggest effect. The UK's National Health Service (NHS) says that moving more, keeping a healthy weight and eating less sugar and more fibre can delay or even prevent type 2 diabetes.

If you already have your report, upload it to your free MentorSano account. You see HbA1c next to glucose, cholesterol and your other results, with the explanation checked by a pharmacist.

What can make the result higher or lower than it really is?

Because the test depends on red blood cells, anything that changes their lifespan can change the result:

• iron-deficiency anaemia can give somewhat higher values;
• recent blood loss, a transfusion or pregnancy can give lower values;
• some inherited haemoglobin variants can interfere with certain lab methods;
• kidney or liver disease can also affect the value.

In these situations your doctor relies more on blood glucose or asks for other tests.

What symptoms can high blood sugar cause?

Most of the time, at first, none. When blood sugar rises a lot, you may notice:

• strong thirst and a dry mouth;
• needing to pee often, especially at night;
• tiredness;
• blurred vision;
• cuts that are slow to close or infections that keep coming back;
• losing weight without trying.

If you have these signs, don't wait for a routine check-up. See a doctor.

What can you do if your HbA1c is borderline?

What you change	Why it helps
More movement, especially after meals	muscles use glucose from the blood; a 10–15 minute walk after a meal helps
Fewer sugary drinks and juices	liquid sugar raises blood sugar quickly and doesn't fill you up
Whole grains instead of white bread	fibre slows the rise in blood sugar
Vegetables at every meal	they fill your plate with fewer calories and more fibre
Enough sleep	short sleep makes the body less sensitive to insulin
A few kilos less, if you carry extra weight	even a small weight loss improves blood sugar

You don't have to change everything at once. Pick two things from the table that you can keep up, and repeat the test when your doctor says, usually after three months. HbA1c needs time to show a change, because it reflects the past few months.

How often is the test repeated?

If your value is normal and you have no risk factors, your doctor may ask for it every few years. With prediabetes, usually once a year or more often. With diabetes, the test is done several times a year to see how treatment is going. Your doctor sets the schedule based on your situation.