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HbA1c: the three-month average — reference ranges
Glycated haemoglobin: the share of red blood cells with glucose attached. Because red cells live about 120 days, HbA1c reads like a three-month average — it cannot be faked by one good day.
| Bande | mmol/L | mg/dL | Ce que cela signifie |
|---|---|---|---|
| Normal | under 5.7% | under 39 mmol/mol | The expected range in someone without diabetes. |
| Prediabetes | 5.7-6.4% | 39-47 mmol/mol | The three-month average has moved above normal but not into the diabetic range. |
| Diabetes | 6.5% or above | 48 mmol/mol or above | On a standardised laboratory test, 6.5% (48 mmol/mol) or higher is the diagnostic threshold for diabetes. |
| Treatment target | around 7% | around 53 mmol/mol | The ADA's general target for many adults with diabetes, individualised — some aim tighter, some looser, by age and other conditions. |
Le lire en contexte
HbA1c is reported two ways: as a percentage and as mmol/mol (IFCC units, standard across the EU). The percentage is not a blood-sugar average divided by anything — the "estimated average glucose" is a separate conversion, and a 7% HbA1c corresponds roughly to an average glucose of 8.6 mmol/L (154 mg/dL).
Anything that shortens red-cell life — blood loss, donation, some anaemias, pregnancy — makes HbA1c read falsely low, and anything that lengthens it reads falsely high. That is why clinicians sometimes prefer fasting or OGTT values, and why no single number is a diagnosis on its own.
Quand voir un clinicien
- HbA1c 5.7% (39) or above on a lab test — the standard response is a conversation and often a repeat test.
- HbA1c 6.5% (48) or above — needs a formal diagnosis and a care plan.
Référence seulement, pas un diagnostic. Les seuils de cette page sont des valeurs OMS et ADA au niveau population ; votre clinicien interprète vos propres chiffres contre votre histoire, vos médicaments et d’autres tests. Si une valeur vient avec des symptômes, ou continue de bouger dans le mauvais sens, c’est le signal d’agir — pas cette page.