Daily health

What is HbA1c?

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Medically approved by Dr Earim Chaudry
Chief Medical Officer
iconLast updated 7th January 2022
In 30 seconds…

What is HbA1c? the HbA1c is the name of a blood test that measures blood glucose levels. As such, it is a crucial test for those with diabetes – or those who are at risk of the condition.

Specifically, HbA1c measures for glycated haemoglobin. That’s the name of the compounds that haemoglobin – your red blood cells – make with glucose, or the sugar in your blood.

The HbA1c is a convenient test for people who are diabetic because it reveals your blood glucose control over 2 to 3 months. As a result, it can give you visibility over the full history of your blood sugar health. And this is what you want if you are going to tackle the condition.

HbA1c: The Test to Monitor Blood Sugar Levels

If you’re diabetic – or if your doctor has said that you are at risk of diabetes – frequent blood tests will be a big part of your life. To monitor and control the disease effectively, you will need to know what is going on at a chemical level in your blood. And that’s where the HbA1c test comes in.

So, what is HbA1c? While there are a couple of tests that measure the amount of glucose in your blood, the HbA1c measures your average blood sugar levels over time (the last 3 month period). And, by doing so, it gives you the fullest picture of your diabetes.

In this article, we’re going to look at HbA1c in detail. Importantly, HbA1c is both the test itself and the substance in your body that the test monitors. Here, we’ll look at both, as well as what a healthy HbA1c level looks like. 

What is the HbA1c Test?

The HbA1c test is used in the monitoring and treatment of diabetes – both type 1 diabetes and type 2.

Diabetes (or diabetes mellitus) is the condition in which the body is unable to properly turn food into energy. In healthy people, our food is converted into glucose and enters into our bloodstream. And, usually, the hormone insulin is created to help glucose enter our body’s cells. However, in diabetic people, not enough insulin is produced (or it can’t be used effectively) and this means glucose builds up in your blood.

An essential part of diabetes control is measuring just how much glucose is in your blood. And that is what the HbA1c test does — and does well.

Where the finger-prick blood test, for example, can show you your blood sugar levels in a given moment, the HbA1c shows your average blood glucose levels over about 2 to 3 months. This way, a healthcare professional can give you a more informative picture of what is happening inside you.

What is HbA1c Exactly?

So, the HbA1c test measures your blood sugar levels over time. All clear. But what is HbA1c exactly, and why is it called that?

Haemoglobin is a substance in red blood cells that carries oxygen to tissues. Sugar in the blood can attach to it, forming a substance called glycated hemoglobin, or Hemoglobin A1C. Specifically, the HbA1c test measures the level of glycated haemoglobin in your blood sample. 

Haemoglobin is the scientific name for your red blood cells, the proteins in your blood that carry oxygen. When your body is not producing enough insulin – or if your insulin is not being used effectively by your body – more glucose sticks to these haemoglobin cells. Or, to put it in those technical terms again, more of the haemoglobin proteins become glycated. That means that you will have more compounds of haemoglobin and glucose in your blood.

Again, all simple enough. But that A1c? Well, you don’t have only one type of haemoglobin in your blood. Instead, you’ve got A1a, A1b, A2, and other types, too. A1c is the most common type and, as a result, it gives you a more accurate reading.

Finally, what’s important is that these haemoglobin proteins hang around in your blood for about 2 to 3 months. Every test, therefore, gets an insight into what’s been happening in your blood over that period. And that’s useful when it comes to checking if your condition is stable.

That’s why the NHS recommends you do the test every 3 to 6 months.

What is a Good HbA1c Result?

So, now you know what the HbA1c tests for and why it’s important. But we’re still missing a crucial detail. What is the normal HbA1c level? And what happens if yours is too high?

Well, firstly, your normal levels of HbA1c are going to depend on whether you are diabetic, at increased risk of diabetes, or if you have normal blood sugar levels.

For healthy adults without diabetes, your HbA1c results will be below 42 mmol/mol, or 6%. People with diabetes are those with HbA1c results of over 48 mmol/mol, or 6.5%. If you have diabetes, you’ll be expecting your results to be as close to this number as possible.

Anyone who has results that sit between these two figures – so 42-47 mmol/mol, or 6.0-6.4% – may have what we call prediabetes. This is where your blood sugar levels are higher than normal, but not yet high enough to be considered type 2 diabetes proper. However, for everyone who is not diagnosed as diabetic, your target range is below 42 mmol/mol.

What is mmol/mol?

This stands for millimoles per mole and it’s the standard measurement for glucose levels (moles are the chemical unit that describes the relationship between the number of molecules in a chemical and the amount of that substance).

Before that, a percentage was used to give you your HbA1c test results. That’s why you’ll sometimes see that 6%, 6.5%, or somewhere in between.

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Key Takeaways

To recap: What is HbA1c? It’s the test that measures the amount of glycated haemoglobin in your blood – and it’s a crucial test in the control and treatment of diabetes.

Anything over 48 mmol/mol means that you are officially classed as diabetic. And that means you have a much higher level of sugar in your blood than normal.


While we've ensured that everything you read on the Health Centre is medically reviewed and approved, information presented here is not intended to be a substitute for professional medical advice, diagnosis, or treatment. It should never be relied upon for specific medical advice. If you have any questions or concerns, please talk to your doctor.

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