Metabolic . Patient guide
Glycated Haemoglobin (HbA1c) Blood Test
Also known as: Glycohaemoglobin, A1c
What is HbA1c
HbA1c is haemoglobin that has reacted with glucose in the bloodstream, and the blood test reflects average blood glucose over the previous 8 to 12 weeks. According to NICE NG28 (Type 2 diabetes in adults), an HbA1c below 42 mmol/mol (6.0%) is normal, 42 to 47 mmol/mol (6.0 to 6.4%) is non-diabetic hyperglycaemia at risk of progression, and 48 mmol/mol (6.5%) or above is diagnostic of diabetes (typically requiring confirmation on a second occasion unless the patient is symptomatic). Approximately 1 in 10 UK adults has type 2 diabetes or pre-diabetes, with prevalence rising sharply over the age of 50.
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.
Symptoms often investigated with Glycated Haemoglobin
Glycated Haemoglobin is commonly tested when patients present with the following symptoms. If any of these resonate with you, the linked guides explain what to look for and which test pathway is appropriate.
Read this marker alongside another
Glycated Haemoglobin is most useful when interpreted together with the markers below. Each guide walks through the 4-quadrant matrix our clinicians use when both come back at once.
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.
Common questions about HbA1c
What is a normal HbA1c range?
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. Always interpret your own results against the laboratory range printed on your report, since assay-specific reference ranges vary.
What does a low HbA1c result mean?
Recent significant blood loss, anaemia (shortens red cell lifespan), some haemoglobinopathies. Not usually a clinical worry on its own.
What does a high HbA1c result mean?
Pre-diabetes or type 2 diabetes. A single elevated result requires confirmation, usually by a second sample, before a diabetes diagnosis is made.
Do I need to fast or prepare for the HbA1c blood test?
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.
Can I order a HbA1c blood test privately in London?
Yes. WMG Health offers HbA1c as part of bespoke panels and several pre-built panels at our 134 Harley Street clinic. Results are clinician-reviewed by a GMC-registered doctor within 4 hours for the most common assays. All panels are custom-built around your specific question; bookings via /contact/ or 020 3239 3378.