HbA1c Calculator

Convert HbA1c % to estimated average blood glucose (mg/dL & mmol/L). Includes ADA risk classification and IFCC conversion.

Normal range: 4–5.6%. Prediabetes: 5.7–6.4%. Diabetes: ≥ 6.5%.

Examples:

Results

ADA Classification

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HbA1c (NGSP)

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eAG (mg/dL)

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eAG (mmol/L)

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IFCC (mmol/mol)

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Risk Level

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4%5.7% Prediabetes6.5% Diabetes14%

▲ Your value on the risk scale

Enter your HbA1c above to see your results.

HbA1c Reference Chart

HbA1c % IFCC (mmol/mol) eAG (mg/dL) eAG (mmol/L) Classification

Frequently Asked Questions

HbA1c (glycated haemoglobin) is a blood test that measures the percentage of haemoglobin coated with sugar over the past 2–3 months. Because red blood cells live roughly 90 days, HbA1c reflects your average blood glucose level over that period, making it far more informative than a single fasting glucose reading.

According to the ADA: below 5.7% = normal; 5.7–6.4% = prediabetes; 6.5% and above = diabetes. For people already diagnosed with diabetes, a target of below 7% is generally recommended to reduce the risk of complications such as retinopathy, nephropathy, and neuropathy. Individual targets may vary — consult your healthcare provider.

The ADA/ADAG formula: eAG (mg/dL) = 28.7 × HbA1c% − 46.7, or in mmol/L: eAG = 1.594 × HbA1c% − 2.594. This was derived from the ADAG study which compared continuous glucose monitoring data to HbA1c values in 507 adults. The IFCC formula converts to mmol/mol: IFCC = (HbA1c% − 2.152) / 0.09148.

There are two standardisation systems: NGSP (% system, used in USA and many other countries) and IFCC (mmol/mol, used in UK and Europe). A reading of 7% NGSP = 53 mmol/mol IFCC. Both measure the same thing but use different scales. Most labs now report both values, and your lab report should specify which system was used.

Yes. HbA1c can be falsely high or low in conditions affecting red blood cell lifespan or haemoglobin structure: haemolytic anaemia (low RBC lifespan → falsely low A1c), iron deficiency anaemia (falsely high), kidney disease, haemoglobin variants (HbS, HbC), and recent blood transfusions can all distort results. In these situations, continuous glucose monitoring or fructosamine testing may be more accurate.

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What Does HbA1c Measure?

When glucose circulates in the bloodstream, it attaches to haemoglobin (the protein in red blood cells). This attachment — called glycation — is irreversible and persists for the life of the red blood cell, roughly 90 days. The HbA1c test measures what percentage of your haemoglobin is glycated, giving a 2–3 month retrospective picture of blood glucose control.

Estimated Average Glucose (eAG)

The ADAG study (2008) derived a regression formula to translate HbA1c values into estimated average glucose (eAG) in the same units used on home glucose meters (mg/dL or mmol/L). This makes HbA1c results more interpretable for patients — a result of "an average blood sugar of 154 mg/dL" is more intuitive than "7% A1c."

Reducing HbA1c

For prediabetes or diabetes management, evidence-based strategies include:

  • Weight loss of 5–10% of body weight (in those who are overweight)
  • 150+ minutes of moderate aerobic exercise per week
  • Reducing refined carbohydrates and added sugars
  • Medications (metformin, GLP-1 agonists, etc.) as prescribed
  • Regular blood glucose self-monitoring

Each 1% reduction in HbA1c reduces the risk of microvascular complications (eye, kidney, nerve damage) by approximately 25–40%.