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Guide to Understanding HbA1c

Adam Bataineh, MD

Longevity MD


A HbA1c test is used to diagnose diabetes and monitor blood glucose control. This guide will help you understand HbA1c so that you can evaluate your metabolic health and make necessary lifestyle changes to push diabetes into remission. 💪

What is a HbA1c measurement?

HbA1C is a measurement of how much glucose is attached to haemoglobin in the blood. Haemoglobin is a protein, which is found in the red blood cells. It’s function is to deliver oxygen around the body. Glucose is also attached to haemoglobin, and can become become sticky (this is called glycation).

Haemoglobin survives for 8–12 weeks before renewal. This is a key feature of the HbA1c test that illustrates the average blood glucose level over a three month period — the more glucose in the blood, the more it will attach to haemoglobin, and the higher HbA1c test will be.

How to test for HbA1c?

To measure HbA1c, a blood sample is taken and sent to the lab for analysis. A HbA1c test can be arranged with your doctor, every 3 months. It is essential to leave at least 3 months in between test as this allows a complete turnover of glycated haemoglobin.

What is a normal HbA1c result?

If you've received your HbA1c result, you can use this guide to interpret your numbers and understand your metabolic health. Please note that the  HbA1c ‘cut off’ range is different between the UK and America.

Normal HbA1c range :

In the UK, 41 mmol/l (5.9%) or less is a normal HbA1c reading

In America, 38mmol/l (5.6%) or less is a normal HbA1c reading

Prediabetes HbA1c range :

In the UK, anything between 42–47 mmol/l (6.0 –6.4%) indicates prediabetes

In America, anything between 39–47 mmol/l (5.7–6.4%) indicates prediabetes.

Diabetes HbA1c range :

In the UK and America, readings 48 mmol/l (6.5% ) or greater, indicates diabetes.

Remission from type 2 diabetes is defined as having a HbA1c level of 48mmol/mol (6.5%) or less, without medication, for a period of time.

Does HbA1c confirm diagnosis?

Not necessarily all the time. Anything that extends or shortens the lifespan of haemoglobin can give a false reading for HbA1c. Iron deficiency or B12 anaemia will result in a false increase as red blood cell turnover is reduced. Haemorrhaging, blood letting or pregnancy will give a false decrease due to shorter haemoglobin lifespan. If any of these conditions apply, then an oral glucose tolerance test (OGTT) or a fasting plasma glucose test (FPG) would be more appropriate for testing pre-diabetes, diabetes or gestational diabetes.

HbA1c test is a powerful tool for diagnosing and monitoring blood glucose as it provides a long term trend of how high your blood sugar levels have been over a period of time. This is different to a blood glucose measurement, which measures the level of glucose at a specific time point. Many factors like sleep, stress or exercise can influence blood glucose measurement, so for this reason a HbA1c test is more informative and reliable. A HbA1c test is generally accurate, however we recommend you use FPG and OGTT as a conjugate for monitoring and diagnosing diabetes. If an individual is asymptomatic, two separate HbA1c tests may also be appropriate.

Together, HbA1c, FPG and OGTT are important measurements for assessing metabolic health. If you start eating a low-carb, high fat diet and practice intermittent fasting, you will most likely see an improvement in all of these. We recommend you regularly test HbA1c to motivate health improvements and to keep track of progress.

If you've experienced an improvement in your HbA1c, please feel free to let us know or post your success on the facebook group — we'd love to hear from you!

Like what you’re hearing?

Stay tuned for more guides, to help you with your health journey.

Take care 👋

I’m sure you’re curious about the science behind all this 🔬 Here are some recent medical publications about this topic:




September 8, 2021
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