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HbA1c
The proportion of haemoglobin that has glucose attached to it. Because red cells live about three months, HbA1c averages blood glucose over roughly the previous eight to twelve weeks, weighted towards the most recent weeks. That makes it the standard measure of longer-term glucose control, and it does not require fasting.
General information only — not a diagnosis, not treatment and not a substitute for your doctor. Reference ranges differ between laboratories, so the range printed on your own report is the one that counts, and only a clinician who knows your history can say what a result means for you. Never start, stop or change a medicine or supplement based on this page.
Usual adult reference range
The ranges below are typical adult reference intervals. Your own laboratory sets its own, printed next to your result, and that is the one to compare against.
| Group | SI units (mmol/mol) | Conventional (%) |
|---|---|---|
| Normal | below 42 | below 6.0 |
| Raised risk / prediabetes range | 42-47 | 6.0-6.4 |
| Diabetes threshold | 48 or above | 6.5 or above |
Source: Commonly used diagnostic thresholds published in clinical guidelines and by laboratories; HbA1c is standardised in mmol/mol (IFCC) with a defined conversion to the older percentage (DCCT) unit. · checked 2026-09-02
What a high result generally indicates
A raised HbA1c means average glucose has been higher than usual over recent months. Above the diagnostic threshold it is one of the accepted ways to diagnose diabetes — but diagnosis normally needs a repeat test or a second abnormal test, and that is a clinician's call, not a calculator's.
What a low result generally indicates
A low HbA1c is rarely a concern on its own. It can appear when red cells are short-lived — haemolysis, recent bleeding, some anaemias — because there has been less time for glucose to attach. In those situations HbA1c is unreliable in both directions and other glucose tests are used instead.
These are general patterns, not a diagnosis. Many things cause a high or low result, and the same figure means different things in different people. What yours means is a question for the doctor who ordered the test.
What affects this result
- Anything that shortens red cell life (haemolysis, recent blood loss, some anaemias) lowers it.
- Iron deficiency anaemia can raise it slightly, independent of glucose.
- Haemoglobin variants interfere with some assays; laboratories flag this.
- Pregnancy changes red cell turnover, so different criteria are used.
- Chronic kidney disease and recent transfusion both distort it.
- Diet and activity move it, but slowly — weeks, not days.
Before the test
No fasting needed; it can be taken at any time of day.
Any preparation instruction that comes with your test slip overrides this general note — follow the one your clinician or laboratory gave you.
The one thing to take from this page
The range above is a typical interval for orientation. Your own laboratory's range, printed beside your result, is the one that applies to you — and a result is only meaningful alongside your symptoms, your history, your medicines and your other tests. That reading is a clinician's job. This page cannot diagnose anything, cannot tell you to change a medicine or a supplement, and is not a substitute for the person who ordered your test.
Frequently asked questions
What is the normal range for hba1c?
A typical adult reference interval is below 42 mmol/mol, but laboratories differ — the range printed on your own report is the one to use. And a result inside or outside a range is only meaningful in context, which is your doctor's reading, not a web page's.
What does a high hba1c mean?
A raised HbA1c means average glucose has been higher than usual over recent months. Above the diagnostic threshold it is one of the accepted ways to diagnose diabetes — but diagnosis normally needs a repeat test or a second abnormal test, and that is a clinician's call, not a calculator's.
What does a low hba1c mean?
A low HbA1c is rarely a concern on its own. It can appear when red cells are short-lived — haemolysis, recent bleeding, some anaemias — because there has been less time for glucose to attach. In those situations HbA1c is unreliable in both directions and other glucose tests are used instead.
Other markers
Haemoglobin
Hb, HGB
Ferritin
Serum ferritin
Vitamin D (25-OH)
25-hydroxyvitamin D, calcidiol
Fasting glucose
Fasting plasma glucose, FPG
Total cholesterol
TC
LDL cholesterol
LDL-C, "bad" cholesterol
All markers and the checker · Symptoms and nutrients · Medicine interactions
Bring context to your next result
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