The HbA1c blood test is a measure used to diagnose diabetes. However, even at pre-diabetic levels and below, there’s a lot that the HbA1c can tell us about our body’s ability to use carbohydrates and sugars.
In this article, we’ll take a look at what the HbA1c blood test shows, how to interpret the results, how you can use your HbA1c levels as a guide to your ideal macronutrient ratio, and how other lifestyle factors can influence the HbA1c.
What is the HbA1c blood test?
The HbA1c test is a simple blood test that measures your average blood glucose level over the last 90 days. An HbA1c finger prick blood test is a quick and non-invasive test that can be quickly processed to deliver the results. The results of an HbA1c test can be used to:
- Diagnose diabetes
- Assess diabetes risk
- Check how well your existing diabetes medications are working
- Track how diabetes might affect your long-term health
- Offer insights into optimal macronutrient ratios in your diet
Unlike a straightforward glucose test (which is often done after fasting for 12-16 hours), you don’t need to fast prior to having an HbA1c blood test. Since the HbA1c shows an average of the amount of glucose present in your blood over the last 90 days, eating prior to the test is unlikely to have a significant impact on the result.
What does an HbA1c test show?
HbA1c is looking at markers on the Haemoglobin in our blood. When our blood sugars are raised, that leaves an imprint on the blood. When blood sugar is raised repeatedly, it leaves multiple imprints. These are like high-water marks on a pier. We can look at the blood record and effectively determine how often the blood sugar has been high, and how high it’s been. Half our blood cells die and are replaced with new ones over the course of 30 days, so over 3 months, we have a totally different set of blood cells than we did at the start, and this is why we don’t recommend frequent HbA1c tests, or at least not before a good percentage of the blood has changed over in this natural process of replenishment.
It’s important to understand what it can and can’t tell us about our health. First, it can’t tell us the precise amounts of glucose, insulin, and other hormones present in the blood. To do that, you’d need a blood draw and insulin pump test, and that’s not what HbA1c is designed to do. Second, if it were to show a high reading, in the diabetic range for example, it can’t tell us the precise cause of that diabetes, only that there are markers on the Haemoglobin which indicate prolonged or repeated elevated blood sugar over the last 90 days. Even though it’s possible to use an HbA1c test to diagnose diabetes, it’s not an exact science, and should not be the sole test done to come to a diagnosis. Third, HbA1c testing is most useful for assessing diabetes risk and what might happen if you were to develop diabetes.
How to interpret the results
Broadly speaking, the closer a reading is to 0, the better, though no-one can ever really expect a reading of 0. It’s important to note that HbA1c is only a numerical representation of average blood glucose levels. It does not tell us how high or low glucose was at any given time. It is also important to take into account any factors that could affect your reading, such as if you’re pregnant, if you’re eating a large amount of sugar, if you’ve taken certain medications, etc. If your HbA1c is between 39mmol/l (5.7%) and 48mmol/l (6.5%), you have an elevated risk of developing diabetes.
How to use the results to make lifestyle changes
If your HbA1c is above trace but normal or below 48mmol/l (6.5%), there’s no need to stress out. You do not have diabetes. However if you are looking to optimise your diet for fat loss and general health, we categorise the ‘normal’ range into a number of ranges, and apply some lifestyle changes which will help you do that.
If you have a level of 48mmol/l (6.5%) or above, this is an elevated risk level and we will advise you to talk to your GP if this is new information to you. One of the first things to do is to get your HbA1c under control.
If you don’t have diabetes, but your HbA1c is below but approaching 48mmol/l (6.5%), we will send you away with some dietary considerations. In general, the higher your HbA1c level is, the more we would advise limiting first simple sugars, then limiting carbohydrates overall, and as we approach the limit we might suggest things like consolidating meals into fewer instances of eating, or implementing time-restricted-feeding. all these measures are aimed at giving your body a break from blood sugars and allowing insulin levels to come to baseline for longer periods of the day.
Interestingly, other interventions like stopping smoking or swapping out processed foods for whole foods all have a positive impact on HbA1c. Overall, having a greater amount of muscle mass also helps.
HbA1c testing is a useful tool that can help to assess your diabetes risk and report on your average blood glucose levels over the past 90 days. It can’t tell us the precise amounts of glucose, insulin, and other hormones present in the blood. It also can’t tell us the precise cause of diabetes. With it, and combined with our dexa scan, we can give a more accurate blueprint of the kind of diet which may work for you to address any fat loss or recomposition goals, or indeed how to better eat for health and longevity.
Want to read more?
The following articles and studies were used to write this article, and so you might gain further insight by reading some in full: