Biomarker · Metabolic
HbA1c (glycated haemoglobin)
HbA1c reflects your average blood sugar over roughly 2–3 months. Learn what the test measures, how it's used to screen for diabetes and what affects accuracy.
Written by LON6EVITY Editorial Team · Last updated
Overview
HbA1c measures the percentage of haemoglobin in red blood cells that has glucose attached. Because red blood cells live around three months, HbA1c reflects average blood glucose over the previous 2–3 months.
Why it matters
HbA1c is used to screen for and diagnose prediabetes and type 2 diabetes and to monitor glucose control. WHO notes that diabetes is a major cause of blindness, kidney failure, heart attacks and stroke, so early detection matters.
Higher results
Higher HbA1c indicates higher average glucose. According to NIDDK, results in the prediabetes range signal increased risk of developing type 2 diabetes. A diagnosis requires confirmation by a clinician.
Factors affecting accuracy
Conditions that change red blood cell lifespan — anaemia, recent blood loss or transfusion, some haemoglobin variants, pregnancy and kidney disease — can make HbA1c misleading.
How the test is performed
A standard blood sample; no fasting required.
Reference ranges
| NIDDK: normal | < 5.7% (< 39 mmol/mol) |
|---|---|
| NIDDK: prediabetes range | 5.7–6.4% (39–47 mmol/mol) |
| NIDDK: diabetes range | ≥ 6.5% (≥ 48 mmol/mol) |
Reference ranges and targets differ between laboratories, units and guidelines, and depend on age, sex, method and your overall clinical picture. A single result is not a diagnosis — interpret it with a qualified clinician.
Factors that can affect the result
- Anaemia and iron deficiency
- Haemoglobin variants
- Pregnancy
- Kidney disease
- Recent transfusion
Questions people commonly ask
- Do I need to fast for HbA1c?
- No. HbA1c reflects a longer period, so fasting is not needed.
- How often is HbA1c checked?
- It depends on your situation. People without diabetes are screened at intervals set by local guidelines; people with diabetes are often tested every 3–6 months.
Related biomarkers
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Understand your biomarkers in context
What does this mean for your own health data? Log your results, follow trends over time and bring an organised summary to your next doctor's appointment.
Sources
- Hemoglobin A1C (HbA1c) Test. MedlinePlus, U.S. National Library of Medicine.
- Diabetes Tests & Diagnosis. National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK).
- Diabetes fact sheet. World Health Organization.