HbA1c is one of the most useful single numbers you can know about your health — and most people have never heard of it. If your blood sugar were a stock market, HbA1c is the three-month average; a snapshot of how your body has been managing glucose for the past 8–12 weeks.
What is HbA1c?
HbA1c stands for glycated haemoglobin. Haemoglobin is the protein in your red blood cells that carries oxygen. When sugar is in your blood, some of it sticks to haemoglobin permanently. The longer there's high sugar around, the more haemoglobin gets coated.
Because red blood cells live for about three months, an HbA1c test gives you a moving average of your blood sugar over that period. A single fasting glucose reading tells you what your sugar is doing right now. HbA1c tells you what it's been doing for weeks.
Why does it matter?
According to the latest figures from Diabetes UK, more than 5 million people in the UK are living with diabetes — and another 6.3 million have prediabetes (raised sugar that hasn't yet tipped into diabetes). The vast majority of prediabetes goes undiagnosed because it has no obvious symptoms.
HbA1c is the test most often used to spot it. The earlier raised sugar is identified, the easier it is to address through diet, exercise, weight, and sleep — long before medication enters the picture.
What do the numbers mean?
HbA1c is reported in mmol/mol in the UK. Roughly:
- Below 42 mmol/mol — typical range
- 42–47 mmol/mol — raised (sometimes called "prediabetes")
- 48 mmol/mol or above — the threshold the NHS uses to diagnose Type 2 diabetes
What's interesting is that HbA1c sits on a continuous scale. Someone at 41 isn't dramatically different from someone at 43, but those two numbers fall on different sides of the "raised" line. That's why monitoring trends over time is more useful than fixating on a single reading.
Three things you might not know about HbA1c
1. It's affected by how long your red blood cells live
The standard assumption is that red blood cells live ~120 days. If you have anaemia, certain genetic conditions, or you've recently lost blood, your cells may live shorter or longer than average. This can skew HbA1c slightly. It's one reason results are interpreted alongside other markers like ferritin and a full blood count.
2. Coffee, fasting, and exercise on the morning of your test don't change it
Unlike a fasting glucose test, HbA1c reflects months of average sugar — so a single morning's behaviour barely moves it. You don't need to fast before the test. You don't need to skip your coffee.
3. Lifestyle changes show up on the test surprisingly fast
Because your red blood cells are continuously being replaced, even six to eight weeks of better sleep, lower carbohydrate intake, or more walking can move HbA1c measurably. It's one of the most responsive long-term markers in the body.
Who should consider testing it?
Most adults benefit from knowing their HbA1c, especially if any of the following apply:
- You're over 40
- There's a family history of Type 2 diabetes
- You've had unexplained weight changes or persistent fatigue
- Your waist circumference is above 94 cm (men) or 80 cm (women) — a strong indicator from the British Heart Foundation
- You're starting a new lifestyle programme and want a baseline to track
How to test your HbA1c
HbA1c is included in several Chxhealth panels, including our Diabetes Status, Metabolic Syndrome, and Heart Health panels. You can collect a sample at our County Durham clinic, at a partner clinic across the UK, or — for selected products — with an at-home kit. Results are typically delivered within 3–5 working days as a clear, easy-to-read PDF report.
Browse all our biomarker panels →
This article is informational. Chxhealth is a biomarker and genetic data provider — we do not diagnose, treat or prescribe. If your results are outside typical ranges, talk to your GP or a healthcare professional about next steps.
