A1C Calculator

What Is A1C and Why It Matters

The A1C test (also called HbA1c or glycated hemoglobin) measures your average blood sugar level over the past 2-3 months. Unlike daily glucose readings that capture a moment in time, A1C shows the bigger picture of blood sugar control. Red blood cells live about 120 days, and sugar naturally attaches to hemoglobin in these cells. Higher blood sugar means more sugar-coated hemoglobin. A normal A1C is below 5.7%. Prediabetes is diagnosed between 5.7-6.4%, and diabetes at 6.5% or higher. For most adults with diabetes, the target A1C is below 7%, though your doctor may set a different goal based on your individual circumstances.

A1C to Blood Sugar Conversion Formula

The formula to convert A1C to estimated average glucose (eAG) is: eAG (mg/dL) = 28.7 x A1C - 46.7. This formula was established by the A1C-Derived Average Glucose (ADAG) study and is used by the American Diabetes Association. For example, an A1C of 7% equals an average glucose of approximately 154 mg/dL. To convert to mmol/L, divide the mg/dL result by 18. Conversely, to go from average glucose to A1C: A1C = (eAG + 46.7) / 28.7. These conversions help patients understand their lab results in terms of daily glucose numbers they can relate to.

A1C Targets for Different Populations

The standard A1C target of below 7% applies to most non-pregnant adults with diabetes. However, targets may vary. For otherwise healthy adults with newly diagnosed diabetes, a target below 6.5% may be appropriate. Older adults or those with multiple health conditions may have a more relaxed target of below 8%. Children and adolescents with type 1 diabetes typically target below 7%. Pregnant women with pre-existing diabetes aim for below 6% if possible without significant hypoglycemia. Every 1% reduction in A1C reduces the risk of microvascular complications by roughly 40%.

Factors That Can Affect A1C Results

Several conditions can cause inaccurate A1C readings. Iron deficiency anemia may falsely raise A1C, while hemolytic anemia or recent blood loss can lower it. Certain hemoglobin variants common in some ethnic groups can affect results. Kidney disease, liver disease, and recent blood transfusions may also impact accuracy. In these cases, your doctor may use fructosamine testing or continuous glucose monitoring as alternatives. Testing A1C every 3 months is recommended for people with diabetes whose therapy has changed or who are not meeting goals, and at least twice yearly for those with stable glucose control.