HbA1c value: what your long-term blood sugar says about your health

Your HbA1c value is your average blood sugar over the past two to three months, expressed in mmol/mol. Under 39 mmol/mol is generally normal, 39 to 47 is the prediabetes range, and 48 or higher fits the diabetes criterion. Unlike a single sample, HbA1c catches the trend, not one moment.

Let's be honest: this is arguably the most useful sugar value there is, precisely because you can't fool it. One healthy day before the test won't change your HbA1c. It shows how your sugar really sat over the past months.

What is HbA1c, exactly?

HbA1c stands for glycated haemoglobin. Put simply: part of the sugar in your blood sticks to your red blood cells. The higher your blood sugar was on average, the more sugar sticks to them. Because red blood cells last about three months, it measures your average over that period.

That makes HbA1c different from a fasting glucose, which is a snapshot. Researcher David Nathan showed how you can convert HbA1c into an estimated average glucose, which makes the value more tangible (Nathan, Diabetes Care 2008).

You don't need to fast for it, since a recent meal doesn't change your average over months. That makes HbA1c handy and reliable.

Which HbA1c value is normal?

The grouping in mmol/mol is fairly fixed. This table lays out the roughly used ranges so you can place your own result. It remains a guideline, not a diagnosis.

According to the Diabetes Fonds, a doctor usually confirms a diabetes diagnosis with more than one measurement. A single raised HbA1c is a signal to look further, not a final verdict. It's often combined with your fasting glucose for a fuller picture.

What does HbA1c say in men without diabetes?

Here's the part that's often forgotten: even within the normal range, your HbA1c says something. A value of 37 mmol/mol gives more room than 42 mmol/mol, even though both fall outside the diabetes range. For men who want to adjust early, that's useful information.

A gradually rising HbA1c within the normal range can be an early sign that your sugar balance is under pressure. Combined with belly fat especially, that fits the wider picture from our pillar on blood sugar in men.

Some men also notice less energy or slower recovery with a higher sugar load. Those complaints aren't proof, but it pays to place them next to your HbA1c rather than see them separately.

The nice thing about HbA1c is that you can also use it to track yourself. Measure it each year around the same time and you see whether your value stays stable or slowly climbs. That trend often says more than one single result, precisely because small shifts within the normal range already give direction.

HbA1c and your energy

A long-term raised blood sugar can go together with fatigue, though several factors are always involved. Big sugar spikes and dips can make your energy swing across the day, and HbA1c gives an average backdrop to that.

If you often feel tired without a clear reason, your sugar balance is one of the things to include. It rarely stands alone: thyroid, iron and testosterone play a role too. The role of your hormones is covered in belly fat and your hormones.

The point isn't that HbA1c explains your fatigue, but that it can be one of the puzzle pieces. That's why a doctor rarely has it measured alone.

How do you lower a raised HbA1c?

Because HbA1c is an average over months, it also changes slowly. Consistently fewer fast sugars, more movement and losing weight around your middle can help lower your value over a few months. Don't expect a week-to-week jump.

How to approach that concretely and which values to measure along the way is covered in our piece on lowering blood sugar. To track your HbA1c alongside your glucose, the Diabetes panel brings both into view.

Important: these are general insights, not personal treatment advice. Discuss a raised HbA1c with your GP, who can help you decide whether further steps are needed.

References

• Diabetes Fonds. HbA1c and your blood sugar. 2024. diabetesfonds.nl
• RIVM. Diabetes: figures and context. 2024. rivm.nl
• Nathan DM, et al. Translating the A1C assay into estimated average glucose values. Diabetes Care. 2008. PMID 18540046.

Every blood test result at Caliber includes a professional assessment by a BIG-registered doctor. For treatment decisions, discuss your results with your GP.