Module 2
If you have type 2 diabetes, HbA1c is the number your doctor will talk about at almost every appointment. It's worth understanding properly — not just what the number is, but what it's actually measuring and why it matters.
HbA1c stands for glycated haemoglobin. Haemoglobin is the protein inside red blood cells that carries oxygen around the body. When glucose is present in the bloodstream, some of it attaches to haemoglobin — this is called glycation. The more glucose in the blood over time, the more glycated haemoglobin is formed.
Because red blood cells live for approximately 10-12 weeks before being replaced, HbA1c gives a picture of your average blood glucose over roughly that period. It's not affected by what you ate yesterday or whether you had a stressful morning — it reflects the bigger pattern.
HbA1c is measured in mmol/mol in the UK and as a percentage (%) in the US:
Most people with type 2 diabetes are given a target of 48-53 mmol/mol (6.5-7%), though this varies depending on age, medications and individual circumstances. Lower is generally better, but very low HbA1c on certain medications can indicate hypoglycaemia risk.
This is one of the most common sources of frustration. You make real changes — you improve your diet, you start exercising, you take your medication consistently — and three weeks later your HbA1c looks the same. That's not because nothing is working. It's because HbA1c is a 10-12 week average. Changes you make today won't show fully in your HbA1c for up to three months.
This is why consistency matters far more than short bursts of effort. A good week followed by a poor month will not move your HbA1c in the right direction. Steady, sustained change will.
The most impactful factors, roughly in order:
No single factor does it alone. The combination is what shifts the number.
Here are some questions worth asking your diabetes assistant:
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