6 mins

Everything you need to know about HbA1c

Haemoglobin A1c, HbA1c, A1c… You’ve probably heard these terms before, but what do they actually mean? What is a HbA1c test? What is a “normal” HbA1c level? What can you do to lower your HbA1c? These are great questions. We’ve put together everything you need to know about HbA1c here.

25 May 2023
Vials of blood for laboratory testing

What is HbA1c?

Haemoglobin is the part of your blood that carries oxygen and is what gives your blood its red colour. When glucose is processed by your body and enters your bloodstream, a small amount of it attaches to this haemoglobin, binding with it to produce glycated haemoglobin (commonly known as HbA1c). When your body has trouble using glucose effectively, the amount in your body increases.

If your body can’t use glucose effectively and the amount in your body increases, then more and more glucose will bind to your haemoglobin and increase your HbA1c levels as a result. This is why HbA1c levels are used by your healthcare professional to get an idea of your average blood glucose levels over the last 3 months. Red blood cells are continuously replaced in the bloodstream, and only have a lifespan of between 90 and 120 days, which is why an HbA1c measurement only gives an average over the last 8 weeks.

People with diabetes will have their own target HbA1c as discussed with their healthcare professional. Guidelines from the National Institute for Health and Care Excellence (NICE) say the ideal HbA1c is 48 mmol/mol (6.5%) or lower, however people who are at risk of developing diabetes will generally have a lower target - often 42 mmol/mol (6%) or below. In someone without diabetes, a high HbA1c could indicate they have developed diabetes.

Why is HbA1c important?

Because HbA1c estimates your average blood glucose over a period of time, the higher your HbA1c level is, the more glucose there has been in your blood. This can increase the risk of you developing diabetes-related complications, such as eye, foot and kidney problems.

NICE  recommends nine annual health checks that it is important for people with diabetes to receive. Among these nine health checks is HbA1c, showing how important it is for you and your healthcare professional to make decisions about your diabetes therapy. Because of this your HbA1c should be measured at least once a year, but it may be measured more often depending on your need.

What is the difference between HbA1c level and a blood glucose level?

There are a few differences between HbA1c and a blood glucose level.

HbA1c level

  • Measured by a healthcare professional in a lab from a blood sample
  • Gives an average of blood glucose levels over the previous 2-3 months
  • Gives an idea of longer term diabetes management to help you and your healthcare professional make decisions about your therapy plan

Blood glucose level

  • Checked at home or on the go via a finger prick test using a blood glucose monitor
  • Shows a snapshot of what your current blood glucose level is
  • Gives a reading that can be acted on immediately to make day to day adjustments to your insulin or diet as needed

What does my HbA1c level mean?

Knowing your HbA1c level is one matter, but actually understanding what it means is the important thing. Data isn’t useful if you can’t understand it, right?

Because HbA1c is an average of blood sugar levels, a high or above target HbA1c means that blood sugar levels have been consistently above target over the 2-3 months prior to the HbA1c measurement. This suggests that your current therapy plan may not be working for you and means your healthcare professional can look at making adjustments or changes to help you reduce your HbA1c.

You may find it useful to keep a record of your HbA1c levels, maybe in a diary or electronic logbook, to see if you can spot any patterns or trends. What’s important though, is trying to keep your HbA1c level within your target as much as possible.

Why does my HbA1c level change?

Your HbA1c level will generally vary from measurement to measurement depending on the amount of glucose in your blood. If you’ve had a period of high blood glucose levels over the weeks before the measurement is taken then your HbA1c level will reflect this.

There are some other factors that can impact your blood glucose levels and as a result change your HbA1c level, these include:

  • Illness for a period of time, for example with the flu
  • Some lifestyle changes, such as a change in your activity level
  • If you are feeling stressed or depressed

Some medications, such as steroids, can also impact your HbA1c, as can some medical conditions which affect the red blood cells. Please speak to your healthcare professional if this is the case.

If my HbA1c is above my target, can I reduce it?

It’s important to try and keep your HbA1c level within your target range. We know this isn’t easy, but there is evidence to suggest that every 11 mmol/mol (1%) HbA1c reduction can lead to a significant reduction in the risk of diabetes related complications.1

If your HbA1c is above your individual target, there are a number of things you and your healthcare professional can do to bring it down to target.

  • Exercise more regularly
  • Eat a healthy, balanced diet
  • Stop smoking (if you do smoke)
  • Talk to other people with diabetes to learn from their experiences
  • Look into local or online diabetes education courses you could attend or tools you could use - your healthcare professional may be able to suggest some that would be suitable for you

Your healthcare professional may also review your medication and make some adjustments, they may even make a change to the medication you are taking if you are on oral medications.

Is HbA1c the only measure for diabetes management?

As HbA1c is an average measurement, it doesn’t generally detect day to day variations in your blood glucose. For this reason, it is generally used in combination with a measure of variability, such as time in range or points in range, which show the amount of time spent above or below your target blood glucose range.

As you can see, HbA1c is a really important tool for you and your healthcare professional in managing your diabetes. It is not the only tool, as it will be used in combination with other measures, but it can be very valuable in giving an idea of how well managed your diabetes is. If you are unsure when your last HbA1c level was taken, please contact your healthcare professional to check and see when you should next have one.



Stratton I M et al. Association of glycaemia with macrovascular and microvascular complications of type 2 diabetes (UKPDS 35). BMJ 2000; 321: 405-412. https://doi.org/10.1136/bmj.321.7258.405

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