Understanding Your A1C Test: A Plain-English Guide

What it measures

Sugar in your blood naturally attaches to haemoglobin, the protein in red blood cells. Because red blood cells live about three months, the percentage of 'sugar-coated' haemoglobin reflects your average blood sugar over roughly the past 2–3 months.

Converting A1C to average glucose

A1C can be translated into an estimated average glucose (eAG). Approximate values:

• 5.7% ≈ 117 mg/dL (6.5 mmol/L)
• 6.5% ≈ 140 mg/dL (7.8 mmol/L)
• 7.0% ≈ 154 mg/dL (8.6 mmol/L)
• 8.0% ≈ 183 mg/dL (10.2 mmol/L)

Typical targets

Many adults with diabetes aim for an A1C below 7%, but targets are individual. Older adults or people prone to low blood sugar may have a less strict goal, while some may aim lower. Agree your target with your care team.

When A1C can mislead

Conditions that change red blood cell lifespan — such as anaemia, recent blood loss, kidney disease, pregnancy or certain haemoglobin variants — can make A1C read falsely high or low. In these cases, doctors may rely more on glucose readings or continuous glucose monitoring.

How often to test

People with diabetes who are meeting their goals often test twice a year; those whose treatment has changed or who are above target often test every three months.

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