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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.
| Faixa | mmol/L | mg/dL | O que significa |
|---|---|---|---|
| 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. |
Ler no contexto
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.
Quando ver um clínico
- 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.
Só referência, não um diagnóstico. Os limiares desta página são valores OMS e ADA ao nível da população; o seu clínico interpreta os seus próprios números contra o seu histórico, medicamentos e outros exames. Se um valor vem com sintomas, ou continua a mover-se na direção errada, esse é o sinal para agir — não esta página.