How do I convert HbA1c to average glucose?

The internationally used ADAG formula converts HbA1c to estimated average glucose: average glucose in mg/dL equals 28.7 times your HbA1c minus 46.7. To get mmol/L, divide the mg/dL result by 18. This calculator does the conversion automatically in both directions and both units.

What does an HbA1c of 6.5% mean?

An HbA1c of 6.5% corresponds to an estimated average glucose of about 7.8 mmol/L (140 mg/dL) and is the threshold at which diabetes is typically diagnosed. If you receive this result, your doctor will usually confirm it with a repeat test before making a diagnosis.

How often should HbA1c be checked?

For people with well-controlled diabetes, HbA1c is usually checked every six months. If your treatment has changed or your blood sugar is not at target, it may be checked every three months, since that reflects the lifespan of red blood cells. Your doctor will recommend the right frequency for you.

Can anything affect the accuracy of HbA1c?

Yes. Certain conditions can make HbA1c less reliable, including some forms of anaemia, recent blood loss or transfusion, pregnancy, kidney disease, and certain haemoglobin variants. If any of these apply to you, your doctor may use additional tests to assess your blood sugar control.

Diabetes & Blood SugarGlobal

HbA1c to Average Glucose Converter

Convert your HbA1c percentage to estimated average blood glucose (eAG), or work backwards from your average glucose to HbA1c. Shows results in both mmol/L and mg/dL.

Written byAikins Apreku

Reviewed byDeborah Adotso, General Nurse

Updated June 2026

Your HbA1c (%)

What is HbA1c?

HbA1c, also called glycated haemoglobin or A1c, is a measure of your average blood sugar over the past two to three months. It works by measuring the percentage of haemoglobin — the oxygen-carrying protein in red blood cells — that has glucose attached to it. The higher your average blood sugar has been, the more glucose binds to haemoglobin, and the higher your HbA1c. Because red blood cells live for around three months, HbA1c reflects your longer-term glucose control rather than a single moment.

What is estimated average glucose (eAG)?

Estimated average glucose, or eAG, translates your HbA1c percentage into the same units you see on a home blood glucose meter — mmol/L or mg/dL. This makes HbA1c easier to relate to your daily readings. This converter uses the ADAG (A1c-Derived Average Glucose) study formula, which is the internationally recognised equation linking HbA1c to average glucose. For example, an HbA1c of 7% corresponds to an estimated average glucose of about 8.6 mmol/L (154 mg/dL).

How to interpret your HbA1c

For people without diabetes, an HbA1c below 5.7% is considered normal. A result between 5.7% and 6.4% indicates prediabetes, and 6.5% or higher on two separate tests typically indicates diabetes. For people already diagnosed with diabetes, a common target is below 7%, though your personal goal may differ based on your age, health and treatment — your doctor will advise what is right for you. Lower is not always better, as very tight control can increase the risk of low blood sugar in some people.

Why HbA1c matters

HbA1c is one of the most valuable tools in diabetes care because it shows the bigger picture. A single glucose reading can be high or low for many reasons, but HbA1c reveals the overall trend. Keeping HbA1c within your target range significantly reduces the long-term risk of diabetes complications affecting the eyes, kidneys, nerves, heart and blood vessels. Tracking it over time helps you and your healthcare team see whether your management plan is working and where adjustments might help.

Frequently Asked Questions

For people without diabetes, a normal HbA1c is below 5.7%. A result of 5.7% to 6.4% indicates prediabetes, and 6.5% or higher on two separate occasions usually indicates diabetes. People already managing diabetes often aim for below 7%, though individual targets vary.

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Sources & References

1.Nathan DM, et al. (ADAG Study Group). Translating the A1C Assay Into Estimated Average Glucose Values. Diabetes Care.
2.American Diabetes Association. Understanding A1C and eAG.
3.NHS. What is an HbA1c test?

LifeCheckIQ content is based on peer-reviewed research, recognised clinical guidelines, and authoritative medical sources, and is reviewed by Deborah Adotso, General Nurse, for clinical accuracy.

Medical Disclaimer: This tool is for informational and educational purposes only. Results are not a medical diagnosis. Always consult a qualified healthcare professional for medical advice, diagnosis, or treatment. In an emergency, call your local emergency number or visit the nearest hospital immediately.