HbA1c Explained: Targets, Normal Range & Why Every 0.5% Matters

Diabetes Science · 5 · February 20, 2026

Your HbA1c is the single number that best predicts whether diabetes will damage your eyes, kidneys, nerves, and heart. It is the number your endocrinologist checks every 3 months. And most patients do not actually understand what it measures or why it matters.

What It Is

Hemoglobin is a protein inside red blood cells that carries oxygen. Glucose in your blood sticks to hemoglobin permanently. This glucose-coated hemoglobin is HbA1c. Since red blood cells live 120 days, HbA1c reflects your average blood sugar over 2–3 months. A single glucose reading is a photo. HbA1c is a 3-month documentary.

The Numbers

Below 5.7%: normal. 5.7–6.4%: prediabetes. 6.5% and above: diabetes. Each 1% corresponds to roughly 29 mg/dL in average glucose. So 6% = average of ~126 mg/dL. 8% = ~183 mg/dL. 10% = ~240 mg/dL.

Why Every 0.5% Matters

The UKPDS — the largest, longest diabetes study ever — found that every 1% HbA1c reduction cuts diabetes-related deaths by 21%, heart attacks by 14%, and microvascular complications (eyes, kidneys, nerves) by 37%. Even a 0.5% drop significantly lowers your risk.

Journey for Health's Glucose Tracking computes your estimated HbA1c from daily readings using the Nathan/ADAG formula: (average glucose + 46.7) / 28.7. You do not have to wait 3 months for a lab result to know which direction you are heading.

When HbA1c Lies

Iron deficiency anaemia falsely raises it. Sickle cell trait can falsely lower or raise it. Kidney disease, heavy alcohol use, and recent blood transfusions make it unreliable. If your HbA1c does not match your daily glucose readings, ask your doctor about fructosamine testing — a 2–3 week average using a different mechanism.

Your Target

Below 7% for most adults. Below 6.5% for young, recently diagnosed patients without complications. 7.5–8% may be safer for elderly patients or those with severe hypoglycemia history. Tighter is not always better — the ACCORD trial showed that pushing HbA1c below 6% actually increased mortality. Your target should be set with your doctor, not copied from the internet.