Biomarker Glossary

HbA1c

HbA1c is a UK blood test that measures your average blood sugar (glucose) level over the past 2 to 3 months. It is the standard marker used by the NHS to screen for, diagnose and monitor type 2 diabetes and prediabetes.

Also known as: Glycated Haemoglobin, A1C, Glycosylated Haemoglobin, HbA1C

HbA1c is most informative when read alongside related markers like Glucose and Insulin. A single number rarely tells the whole story. If your reading sits outside the typical range, share the full report with your GP or healthcare professional before drawing conclusions.

What is HbA1c?

HbA1c stands for glycated haemoglobin. It reflects the percentage of haemoglobin, the oxygen carrying protein in your red blood cells, that has glucose attached to it.

Because red blood cells live for around 120 days, HbA1c gives a stable picture of your blood sugar exposure over the previous 2 to 3 months. Unlike a one off finger prick glucose reading, HbA1c is not affected by what you ate that morning or how stressed you are on the day of the test.

In the UK, HbA1c is reported in mmol/mol (the IFCC unit). Older results may be given as a percentage (DCCT unit), and both are used internationally.

Why test HbA1c?

  • HbA1c is the standard test used to screen for and diagnose type 2 diabetes and prediabetes.
  • People already living with diabetes use HbA1c to monitor how well their blood sugar is controlled over time.
  • It is also useful for anyone making lifestyle changes (diet, weight loss, exercise) who wants to track the impact on their metabolic health.
HbA1c is the standard test used to screen for and diagnose type 2 diabetes and prediabetes.

HbA1c normal range (UK)

Result What it means
Below 42 mmol/mol (under 6.0%) Normal
42 to 47 mmol/mol (6.0 to 6.4%) Prediabetes (non-diabetic hyperglycaemia)
48 mmol/mol (6.5%) or higher Diabetes range

Reference ranges are based on the NHS and World Health Organization classification. Individual labs may report slightly different cut offs.

About these ranges. The ranges above are typical UK clinical lab ranges aligned to NHS and Royal College of Pathologists guidance. Your Chxhealth report will show the specific reference range used by our partner lab, Randox, for each marker. Lab ranges vary slightly between providers and assays. Always interpret your results in the context of the range printed on your own report.

What causes high HbA1c?

  • Type 2 diabetes or prediabetes
  • Type 1 diabetes
  • Insulin resistance
  • A diet consistently high in refined carbohydrates and added sugar
  • Long term stress or poor sleep affecting blood sugar regulation
  • Some medications (such as corticosteroids)
  • Cushing's syndrome and other endocrine conditions

What causes low HbA1c?

  • Anaemia or low haemoglobin levels (can falsely lower HbA1c readings)
  • Recent blood loss or blood transfusion
  • Haemolytic anaemia (shortened red blood cell lifespan)
  • Some genetic haemoglobin variants
  • Liver or kidney disease in some cases

Symptoms of high HbA1c

  • Increased thirst and urination
  • Tiredness and low energy
  • Blurred vision
  • Slow healing of cuts or infections
  • Unexplained weight loss
  • Tingling or numbness in hands or feet

Symptoms of low HbA1c

  • Most low HbA1c results are caused by underlying red blood cell conditions rather than low blood sugar itself.
  • If you experience sweating, shakiness, hunger or confusion, these are signs of acute hypoglycaemia and a glucose test (not HbA1c) is the right marker.

How is HbA1c tested?

HbA1c is measured from a small blood sample, either by finger prick at home or via a standard blood draw at a clinic.

Unlike a glucose test, HbA1c does not require fasting. You can eat and drink normally before the test.

Chxhealth samples are analysed by Randox, a UK laboratory accredited by UKAS to ISO 15189. Results are typically delivered in 3 to 5 working days.

How to support healthy HbA1c levels

  • Eat a diet centred on whole foods: vegetables, lean protein, healthy fats, and high fibre carbohydrates such as oats, beans and pulses.
  • Reduce refined sugar and ultra processed foods.
  • Move regularly. Even a short walk after meals helps lower post meal blood sugar.
  • Maintain a healthy weight. Modest weight loss (5 to 10 percent of body weight) has been shown to improve HbA1c significantly in prediabetes.
  • Manage stress and prioritise sleep, both of which affect blood sugar regulation.

These are general lifestyle suggestions. Chxhealth is an information service. For personal medical advice, please speak to a healthcare professional.

Chxhealth panels that test HbA1c

20 Chxhealth biomarker panels include HbA1c. Each is analysed by Randox, a UK laboratory accredited by UKAS. Reports are delivered in 3 to 5 working days.

HbA1c FAQs

Is HbA1c the same as a glucose test?

No. A glucose test measures your blood sugar at one moment in time. HbA1c measures your average blood sugar over the past 2 to 3 months. Most people benefit from looking at both, but HbA1c is the standard marker for diagnosing and monitoring diabetes.

Do I need to fast before an HbA1c test?

No. HbA1c does not require fasting. You can eat and drink normally before the test.

What is a good HbA1c if I have diabetes?

The NHS target for most adults with type 2 diabetes is below 53 mmol/mol (7.0%), though individual targets vary based on age, other health conditions and treatment plan. Always discuss your target with your healthcare professional.

Can lifestyle changes really lower HbA1c?

Yes. Many studies show that diet changes, weight loss and regular activity can lower HbA1c by 10 mmol/mol or more in people with prediabetes or early type 2 diabetes. The earlier you act, the larger the typical effect.

How often should I test HbA1c?

If you are monitoring metabolic health or weight loss progress, every 3 to 6 months is sensible. If you are managing diagnosed diabetes, follow the schedule agreed with your healthcare team.

Often tested with HbA1c

The biomarkers below are commonly investigated alongside HbA1c because they reveal connected aspects of the same physiological picture:

  • Glucose: Fasting glucose gives a same-day snapshot of blood sugar that HbA1c misses.
  • Insulin: Fasting insulin alongside HbA1c reveals insulin resistance before glucose rises.
  • Triglycerides: Often elevated together in metabolic dysfunction.
  • Cholesterol: Lipid markers complete the cardiometabolic picture.

Related reading

Choose the right test for your goal

If you are reading about HbA1c because of a specific health goal, our buying guides walk you through which Chxhealth panels fit:

Sources and further reading

This page is informed by guidance from the NHS, NICE, Royal College of Pathologists and other UK authoritative bodies. For deeper detail or to verify the information, see:

About this page. Last reviewed: 13 May 2026. Next scheduled review: May 2027. This page has not yet been independently reviewed by a clinician. It is written from authoritative UK medical guidance (NHS, NICE, Royal College of Pathologists, peer-reviewed sources) but has not undergone formal clinical sign off.

Important. Chxhealth is a UK information service. We do not diagnose, treat or prescribe. The reference ranges and information on this page are general educational content and should not be used as a substitute for advice from a qualified healthcare professional. For any concerns about your health or results, please speak to your GP or another healthcare professional.