§ Glossary · analytical

HbA1c

Glycated haemoglobin — average blood glucose over the past 8–12 weeks.

HbA1c is the percentage of haemoglobin molecules with a glucose molecule covalently bonded to them. Because the reaction is non-enzymatic and irreversible, and because red blood cells live ~120 days, HbA1c integrates glucose exposure across the past 8–12 weeks. The American Diabetes Association threshold for prediabetes is 5.7%, and for diabetes is 6.5%. HbA1c is the gold-standard chronic glycaemia metric — unaffected by recent meals or activity — but it's slow to respond to intervention (8–12 week lag).

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