Metabolic . Patient guide
Glycated Haemoglobin (HbA1c)
Also known as: Glycohaemoglobin, A1c
HbA1c is haemoglobin that has reacted with glucose in the bloodstream. The blood test reflects the average blood glucose level over the previous 8 to 12 weeks and is the standard first-line marker for type 2 diabetes and pre-diabetes.
This biomarker entry is being clinically reviewed by our team. The factual content draws on UK guidance (NICE, NHS, Royal Colleges and the relevant speciality society where cited).
Reference range
Reported in mmol/mol (also seen as % (old DCCT units)). Final reports always carry the issuing laboratory's range, which is what your clinician will interpret against.
| Group | Range | Note |
|---|---|---|
| Normal | under 42 | mmol/mol (equivalent to under 6.0% in old units) |
| Pre-diabetes | 42 to 47 | 6.0 to 6.4% |
| Diabetes (NICE, on confirmation) | 48 or above | 6.5% or above |
| NHS treatment target for many people with type 2 | 48 to 58 |
What it is
Glucose binds non-enzymatically to haemoglobin in red blood cells throughout their roughly 120-day lifespan. The percentage of glycated haemoglobin reflects average glucose exposure over that period, which makes it less affected by recent meals than a fasting glucose.
Why a clinician would order it
Screening for type 2 diabetes and pre-diabetes (especially when family history, raised BMI, unexplained weight gain, or features of insulin resistance are present), monitoring known diabetes, and as part of wellness or pre-treatment health screening.
If your level is outside the range
Symptoms of low HbA1c
- Rarely symptomatic; very low values may occur in some haemoglobinopathies
What low can indicate. Recent significant blood loss, anaemia (shortens red cell lifespan), some haemoglobinopathies. Not usually a clinical worry on its own.
Symptoms of high HbA1c
- Polydipsia, polyuria, weight loss, fatigue (raised glucose); often asymptomatic in pre-diabetes
What high can indicate. Pre-diabetes or type 2 diabetes. A single elevated result requires confirmation, usually by a second sample, before a diabetes diagnosis is made.
Testing tips
No fasting required (a key advantage over fasting glucose). HbA1c is unreliable in conditions that shorten red-cell lifespan (sickle cell, haemolytic anaemia, recent significant blood loss); fasting glucose or oral glucose tolerance test may be preferred.
Where you can get this tested
Glycated Haemoglobin is included in the following WMG Health panels. Same-day appointments at our Harley Street clinic, with results clinician-reviewed.
Want a specific combination of markers we do not have a panel for? Build a custom panel and our clinicians will design one for you.
Related markers
Sources
UK guidance our clinicians use when interpreting this marker.
This page is general patient information, not personal medical advice. A GMC-registered clinician will review your results and tailor any interpretation to you. See our Editorial Policy for how we write and review content.