HbA1c (Glycated Haemoglobin)

What is HbA1c?

HbA1c stands for glycated haemoglobin — the form of haemoglobin that results when glucose binds irreversibly to the protein inside red blood cells. Because red blood cells live for approximately 2–3 months, the proportion of haemoglobin that is glycated provides a reliable index of average blood glucose concentration over that period.

Unlike a fasting glucose test — which reflects blood sugar at a single point in time and can be influenced by what you ate the previous day — HbA1c smooths out day-to-day fluctuations and gives a far more representative picture of long-term glucose metabolism. This makes it the preferred diagnostic test for type 2 diabetes in the UK, recommended by NICE and the World Health Organization.

HbA1c is expressed in the UK in millimoles per mole (mmol/mol), a standardised unit adopted globally since 2011. Older results may be expressed as a percentage (the NGSP/DCCT scale); a clinician can help you compare values across both systems if needed.

Normal reference range

• Normal: below 42 mmol/mol
• Pre-diabetes (impaired glucose regulation): 42–47 mmol/mol
• Diabetes (on two separate tests): 48 mmol/mol or above

Important: Reference ranges vary between laboratories and depend on individual factors including age, sex, pregnancy status, and medication. Always interpret your result in the context of a clinician review. The Vesey reviews every result before release.

What a high HbA1c may indicate

A result in the pre-diabetic or diabetic range suggests that blood glucose has been chronically elevated. Even a result in the pre-diabetes band warrants action, as it carries a significantly increased risk of progression to type 2 diabetes and early cardiovascular disease. Causes and associations include:

• Type 2 diabetes — insulin resistance means glucose accumulates in the blood rather than entering cells
• Pre-diabetes (impaired glucose regulation) — glucose metabolism is impaired but not yet at the diagnostic threshold for diabetes
• Type 1 diabetes — absolute insulin deficiency; HbA1c is used to monitor rather than diagnose
• Steroid use — corticosteroids raise blood glucose and can push HbA1c into the diabetic range
• Haemolytic anaemia (falsely raised) — iron deficiency without supplementation increases HbA1c disproportionately to actual glucose levels
• Cushing's syndrome — excess cortisol drives glucose production and insulin resistance

What a low HbA1c may indicate

A result well below 42 mmol/mol is generally reassuring, but an unusually low HbA1c in a known diabetic patient may indicate over-treatment with insulin or hypoglycaemic medication. In non-diabetic individuals, a low HbA1c may reflect:

• Haemolytic anaemia — increased red cell turnover means fewer cells have been exposed to glucose long enough to become glycated
• Recent blood transfusion — newly transfused red cells artificially lower HbA1c
• Iron deficiency treated with supplementation — rising red cell production dilutes glycated haemoglobin
• Pregnancy — physiological anaemia and increased red cell turnover lower HbA1c values

Get tested at The Vesey, Sutton Coldfield

HbA1c is measured within the following panels at The Vesey Private Hospital:

• Lipids & HbA1c panel — £149 (cardiovascular and metabolic risk in one draw)
• Diabetes Status panel — focused glucose and HbA1c screen
• Lifestyle Screen — broad health check including HbA1c

No fasting required. Results reviewed by a clinician and released securely, typically within 24 hours. Appointments available Monday–Saturday.

Frequently asked questions

What is a normal HbA1c level?

In the UK, an HbA1c below 42 mmol/mol is considered normal. A result of 42–47 mmol/mol indicates pre-diabetes. A result of 48 mmol/mol or above on two separate occasions is diagnostic of type 2 diabetes.

What is the difference between HbA1c and a fasting glucose test?

A fasting glucose test gives a single snapshot of your blood sugar at one moment in time. HbA1c reflects average blood glucose over the preceding 2–3 months, making it a more stable indicator of long-term glucose control. No fasting is required for HbA1c.

Can HbA1c be affected by conditions other than diabetes?

Yes. HbA1c can be falsely low in conditions causing rapid red cell turnover (haemolytic anaemia, supplemented iron deficiency, or pregnancy). It may be falsely elevated in iron deficiency anaemia (untreated) or vitamin B12 deficiency. Your clinician will consider these factors when interpreting your result.

Do I need to fast before an HbA1c test?

No fasting is required. HbA1c measures the accumulated glycation of haemoglobin over months, so what you eat immediately before the test does not affect the result.

How often should I have my HbA1c checked?

If you have type 2 diabetes, every 3–6 months until stable, then at least annually. If you are at risk of pre-diabetes (overweight, family history, sedentary lifestyle), annual monitoring is reasonable. If you have no risk factors and a normal result, every 2–3 years is typically sufficient.