Printed on 3/17/2026
For informational purposes only. This is not medical advice.
HbA1c (glycated hemoglobin) reflects average blood glucose over the preceding 2–3 months. This converter uses the ADAG (A1C-Derived Average Glucose) study formula to translate HbA1c percentages into estimated average glucose (eAG) in both mg/dL and mmol/L, helping patients and clinicians understand what the A1c number means in terms of daily blood sugar levels. Diabetes significantly increases cardiovascular risk — assess with [ASCVD Risk Calculator](/tools/ascvd-risk) or [Framingham Risk Score](/tools/framingham-risk). Obesity drives insulin resistance — check [BMI Calculator](/tools/bmi-calculator). Chronic kidney disease affects A1c accuracy — monitor with [eGFR Calculator](/tools/egfr-calculator).
Formula: eAG (mg/dL) = 28.7 × HbA1c − 46.7 (ADAG formula)
Input your most recent HbA1c lab result, typically reported as a percentage (e.g., 7.0%). This value is usually available on lab reports or patient portals.
The calculator applies the validated ADAG study formula: eAG = 28.7 × HbA1c − 46.7. This converts the percentage into an estimated average glucose in mg/dL.
Compare your eAG to daily glucose readings. If your A1c is 7.0%, your estimated average glucose is about 154 mg/dL — the number you'd see averaging all your finger-stick or CGM readings.
People with diabetes
Understand what your A1c means in terms of daily glucose numbers. If your A1c is 8%, your average blood sugar is about 183 mg/dL — making the abstract percentage relatable.
Endocrinologists, PCPs, CDEs
Use during clinic visits to explain A1c results to patients by translating them to estimated average glucose levels they can relate to their home monitoring.
CGM users, diabetes technology teams
Compare your continuous glucose monitor's reported average glucose to your A1c-derived eAG. If they differ significantly, it may indicate glycation rate variation or timing issues.
Patients and care teams
Set glucose targets based on A1c goals. To reach an A1c of 7%, you'll need an average glucose around 154 mg/dL — giving you a concrete daily target to work toward.
Cardiologists, primary care
Explain how elevated A1c translates to chronically high blood sugar, which accelerates atherosclerosis. Each 1% increase in A1c corresponds to roughly 29 mg/dL higher average glucose. Quantify 10-year CV risk with [ASCVD Risk Calculator](/tools/ascvd-risk) or [Framingham Risk Score](/tools/framingham-risk).
International clinicians, travelers
Convert between mg/dL (US) and mmol/L (Europe, most other countries) for glucose values when working with international guidelines or traveling patients.
Conditions that shorten red blood cell lifespan (hemolytic anemia, blood loss, chronic kidney disease on EPO — check [eGFR Calculator](/tools/egfr-calculator)) cause falsely low A1c. The glucose hasn't had time to glycate hemoglobin. Fructosamine may be more accurate here.
Conditions that prolong RBC lifespan (iron deficiency anemia, B12/folate deficiency, splenectomy) cause falsely high A1c. The hemoglobin has extra time to accumulate glucose. Check reticulocyte count if suspicious.
Some countries report A1c in mmol/mol (IFCC units) rather than percentage (DCCT/NGSP). To convert: IFCC = (NGSP - 2.15) × 10.929. An A1c of 7% equals 53 mmol/mol.
Two patients with the same A1c can have very different glucose patterns. CGM metrics like time in range (70-180 mg/dL), time below range, and glucose variability provide insights that A1c alone misses.
Per ADA, diabetes diagnosis requires A1c ≥6.5% on two separate occasions, OR one A1c plus a confirmatory test (fasting glucose ≥126, random glucose ≥200 with symptoms). A single A1c is not sufficient.
While A1c represents ~3 months of glucose exposure, the most recent month contributes about 50% of the value. If you've made recent changes, wait at least 6-8 weeks before rechecking.
Hemoglobin S, C, D, E, and other variants can interfere with certain A1c assays. Most modern lab methods (HPLC, immunoassay) can handle common variants, but check your lab's documentation if you have hemoglobinopathy.
In gestational diabetes, A1c is not recommended for diagnosis due to physiological changes in RBC turnover. For management, fasting and postprandial glucose targets are used instead of A1c goals.
The ADA recommends A1c <7.5-8% for older adults with complex health issues, limited life expectancy, or high hypoglycemia risk. Avoiding hypoglycemia is often more important than aggressive A1c reduction.
The ADAG formula gives a quick rule of thumb: dropping A1c by 1% means lowering average glucose by about 29 mg/dL. Use this to help patients understand the impact of medication or lifestyle changes.
The ADAG formula was derived from the international A1C-Derived Average Glucose study (Nathan et al., Diabetes Care 2008) correlating A1c with CGM data in 507 participants. A1c diagnostic thresholds are from ADA Standards of Care 2024. The relationship between A1c and complications is based on DCCT (type 1) and UKPDS (type 2) landmark trials.
Your HbA1c is converted to an estimated average glucose (eAG) so you can relate it to the numbers you see on a daily glucose meter. An HbA1c below 5.7% is considered normal. Values of 5.7–6.4% indicate prediabetes, and 6.5% or higher on two separate tests is diagnostic of diabetes.
For people with diabetes, the American Diabetes Association (ADA) recommends a target HbA1c of less than 7.0% for most adults, which corresponds to an eAG of approximately 154 mg/dL (8.6 mmol/L). More aggressive targets (< 6.5%) may be appropriate for younger patients without significant hypoglycemia risk, while a more relaxed target (< 8.0%) may be acceptable for older adults or those with multiple comorbidities.
Use this converter when reviewing lab results to understand what an HbA1c percentage means in terms of day-to-day blood glucose levels. It is particularly useful for patient education — helping individuals connect the abstract A1c number to the glucose readings they monitor at home.
Clinicians use it during diabetes management visits to set and communicate glycemic targets. It is also helpful when comparing glucose control across different measurement units, as some regions report glucose in mg/dL while others use mmol/L.
HbA1c accuracy depends on normal red blood cell turnover. Conditions that shorten red blood cell lifespan — such as hemolytic anemia, recent blood loss, blood transfusions, or chronic kidney disease treated with erythropoietin — can produce falsely low HbA1c values. Conditions that lengthen red blood cell lifespan, like iron deficiency anemia or splenectomy, can falsely elevate the result.
Hemoglobin variants (HbS, HbC, HbE) may interfere with certain assay methods, though most modern assays can handle common variants. The ADAG conversion formula provides a population average — individual patients may have consistently higher or lower average glucose than their A1c predicts due to genetic variation in glycation rates.
HbA1c should not be used for diagnosis during pregnancy, in patients with recent blood transfusions, or in patients with hemoglobinopathies. Fructosamine or glycated albumin may be better alternatives in these settings.
For related assessments, see Insulin Correction, Framingham Risk and Glycemic Index.
Disclaimer: This tool is for educational and informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider with questions about your health.
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