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Glycated Haemoglobin HbA1c
Related Subjects: |Type 1 DM |Type 2 DM |Diabetes in Pregnancy |HbA1c |Diabetic Ketoacidosis (DKA) Adults |Hyperglycaemic Hyperosmolar State (HHS) |Diabetic Nephropathy |Diabetic Retinopathy |Diabetic Neuropathy
🧪 HbA1c reflects average blood glucose control over ~3 months (lifespan of an erythrocyte 🩸). It provides a long-term marker of glycaemic control compared to daily glucose fluctuations.
ℹ️ About
- 📊 HbA1c reflects integrated blood glucose control over 120 days.
- 🍬 Formed by glucose binding covalently to haemoglobin (HbA beta chain valine).
- 🔄 Sensitive to changes in glycaemic control in the 4 weeks before measurement.
- 📏 Reported in mmol/mol (IFCC). Conversion:
IFCC HbA1c (mmol/mol) = [DCCT HbA1c(%) − 2.15] × 10.929 - ↗️ Rough guide: +11 mmol/mol ≈ +2 mmol/L (36 mg/dL) in mean blood glucose.
🧬 Aetiology
- ⚡ Glycosylation = glucose binds terminal valine of HbA beta chain.
- 📈 Proportional to mean glucose exposure over ~6 weeks.
- 🔹 Fructosamine = glycosylated albumin → reflects control over 2–3 weeks (shorter window).
🎯 Uses
- 🧑⚕️ Guides long-term diabetes management (Type 1 & Type 2).
- 📉 On average, oral hypoglycaemic drugs ↓ HbA1c by ~1%.
- 💊 HbA1c >8% ➝ usually needs pharmacotherapy (not just diet).
HbA1c >9% ➝ consider insulin. - 👩🍼 In pregnancy ➝ Fructosamine is preferred (shorter half-life, avoids misleading HbA1c).
- ⚠️ Falsely low in haemoglobinopathies (e.g., thalassaemia, sickle cell).
📖 Interpretation
- ✅ Normal population: ~4.5–6.5% (25–48 mmol/mol).
- 🎯 Target in diabetes: 6.5–7.0% (realistically 7.0% for many patients).
- 🏥 Clinical Trials:
- DCCT (Type 1 DM): showed HbA1c links to microvascular complications.
- UKPDS (Type 2 DM): confirmed HbA1c as a marker of microangiopathy risk.
- 📐 Standardisation: IFCC/DCCT alignment avoids inter-lab errors.
| The content on this website is provided for educational and informational purposes only to support exam preparation (e.g., MLA, MRCP, USMLE) and learning. This is NOT medical advice, diagnosis, treatment, or professional guidance. It does not replace consultation with a qualified healthcare professional, official guidelines (e.g., NICE, GMC, BNF), or supervised clinical practice. Always verify information with current, authoritative sources. Makindo and its contributors accept no liability for any reliance on this content, including errors, omissions, or any resulting harm, loss, or consequences. By using this site, you agree to these terms. |
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