What Is HbA1c?
HbA1c (glycated haemoglobin, or haemoglobin A1c) is a blood test that gives a picture of your average blood sugar levels over the past 2–3 months. Unlike a fingerstick glucose reading, which shows what your blood sugar is right now, HbA1c reveals the longer-term trend — making it one of the most valuable tools in diabetes monitoring.
Here's how it works: glucose in your bloodstream attaches to haemoglobin (the protein in red blood cells that carries oxygen). The higher your blood sugar over time, the more glucose attaches. Since red blood cells live for about 2–3 months, the test captures a rolling average across that period.
How Is It Measured?
HbA1c results are expressed in two ways depending on where you live:
- Percentage (%): Common in the US, Canada, and Australia.
- mmol/mol: Used in the UK and many European countries.
What Do the Numbers Mean?
| HbA1c (%) | HbA1c (mmol/mol) | What It Indicates |
|---|---|---|
| Below 5.7% | Below 39 | Normal (no diabetes) |
| 5.7–6.4% | 39–46 | Prediabetes |
| 6.5% or above | 48 or above | Diabetes diagnosis |
| Below 7.0% | Below 53 | Target for most adults with diabetes |
| 7.0–8.0% | 53–64 | Acceptable range for some (discuss with doctor) |
| Above 9.0% | Above 75 | High risk — action needed |
Note: Individual targets vary. Older adults, those with frequent hypoglycaemia, or those with complex health needs may have higher personalised targets. Always confirm your goal with your healthcare provider.
Limitations of HbA1c
HbA1c is powerful, but it has real blind spots:
- It doesn't show variability — a person with frequent highs and lows may have the same HbA1c as someone with consistently stable levels.
- Conditions affecting red blood cells (anaemia, sickle cell trait) can give misleading results.
- It's a lagging indicator — changes you make today won't fully show up for weeks or months.
How to Lower Your HbA1c
Improving your HbA1c is about consistently better blood sugar management over time, not one-off actions. Effective strategies include:
- Dietary changes: Reducing refined carbohydrates, eating more fibre, and following a consistent meal pattern help smooth out blood sugar fluctuations.
- Regular exercise: Both aerobic exercise and strength training improve insulin sensitivity, which directly affects long-term glucose levels.
- Medication adherence: Taking prescribed medications consistently and as directed makes a significant difference.
- Frequent self-monitoring: Checking your blood sugar regularly helps you identify patterns and respond to them earlier.
- Sleep and stress management: Poor sleep and chronic stress both elevate cortisol, which raises blood sugar. Addressing these factors is often overlooked but genuinely impactful.
- Working with your care team: Regular reviews allow medication adjustments and personalised guidance as your needs change.
How Often Should You Be Tested?
For most people with diabetes, HbA1c is tested every 3–6 months depending on how well-controlled blood sugar is and whether any treatment changes have been made. If your levels are stable and within target, every 6 months is typically sufficient. If you're working to improve your levels or have recently changed medication, more frequent testing helps track progress.
The Bottom Line
Your HbA1c is a valuable compass — not a verdict. A single high reading isn't cause for alarm; it's information. Use it alongside daily glucose monitoring, your symptoms, and your healthcare team's guidance to make steady, sustainable improvements to your long-term health.