MayoCalc / Health

A1C to Blood Sugar Converter

Convert your A1C (HbA1c) to estimated average glucose (eAG) using the ADA-validated ADAG formula, or convert average glucose back to A1C.

%
A1C
6.0%
Avg. Blood Sugar
126
mg/dL
Normal (<5.7%)Pre (5.7-6.4%)Diabetes (6.5%+)
Category
Normal
Your A1C is in the normal range. This means your average blood sugar over the past 2-3 months has been well controlled.

A1C to Average Blood Sugar Chart

A1C (%)eAG (mg/dL)eAG (mmol/L)Category
5.0975.4Normal
5.51116.2Normal
5.71176.5Prediabetes
6.01267.0Prediabetes
6.51407.8Diabetes
7.01548.6Diabetes
8.018310.2Diabetes
9.021211.8Diabetes
10.024013.4Diabetes

What Is A1C?

A1C (also called HbA1c or glycated hemoglobin) measures the percentage of your red blood cells that have sugar attached to them. Because red blood cells live about 120 days, A1C reflects your average blood sugar over the past 2-3 months, with the most recent 30 days contributing the most. Unlike a fasting glucose test (which captures a single moment), A1C gives a broader picture of your blood sugar control over time.

How the Conversion Works

This calculator uses the ADAG (A1C-Derived Average Glucose) formula published by Nathan et al. in Diabetes Care (2008) and endorsed by the American Diabetes Association (ADA). The formula is: eAG (mg/dL) = 28.7 x A1C - 46.7. The ADAG study included 507 people with type 1 diabetes, type 2 diabetes, and without diabetes across 10 international centers, using over 2,700 glucose measurements per subject over 3 months via continuous glucose monitors and fingerstick profiles.

ADA Targets

For most adults with diabetes, the ADA recommends an A1C target of below 7% (corresponding to an average glucose of about 154 mg/dL), per the 2025 Standards of Care. Tighter targets (below 6.5%) may be appropriate for some patients if they can be achieved without significant low blood sugar episodes. Less strict targets (below 8%) may be reasonable for older adults or those with other serious health conditions.

A1C FAQ

How often should I get my A1C checked?
If your blood sugar is well controlled and stable, twice a year is sufficient. If you have recently changed medications or are not meeting your target, every 3 months is recommended. Your doctor will advise based on your situation.
Why does my A1C not match my home glucose readings?
Home meters measure glucose at a single point in time, while A1C averages everything over 2-3 months, including overnight and post-meal spikes you may not catch. Some people also have naturally higher or lower glycation rates (called "glycation gap"), meaning their A1C runs higher or lower than expected for their actual average glucose. Conditions like anemia, kidney disease, and certain hemoglobin variants can also affect A1C accuracy.
Can I lower my A1C without medication?
Yes, especially in the prediabetes range. The Diabetes Prevention Program study showed that lifestyle changes (150 minutes per week of moderate exercise, 5-7% weight loss, and dietary improvements) reduced the risk of developing type 2 diabetes by 58%. These same changes can lower A1C by 0.5-1.5% in people already diagnosed with type 2 diabetes.
What is a dangerous A1C level?
An A1C above 9% is considered very poorly controlled and significantly increases the risk of complications including nerve damage, kidney disease, vision loss, and heart disease. An A1C above 10% (average glucose over 240 mg/dL) is a medical concern that usually requires prompt treatment adjustment.

Related Tools

🩸

Lab Results Interpreter

CBC, CMP, lipid panel, thyroid

 🩸

eGFR Calculator

Kidney function estimate

 ⚖

BMI Calculator

Check your body mass index
Uses the ADAG formula (Nathan et al., Diabetes Care 2008). Diabetes thresholds per ADA Standards of Care 2025. This tool is for informational purposes only and is not a substitute for medical advice.