HbA1c ↔ estimated average glucose (eAG) calculator

HbA1c, or glycated hemoglobin, shows how much glucose has attached to the hemoglobin in your red blood cells over roughly the past 2–3 months. HbA1c reflects your average blood glucose over this period rather than the value at a single moment. Red blood cells live for about 120 days, but recent glucose levels weigh the most, so HbA1c reflects the last 2–3 months. It is the main indicator used to track long-term diabetes control. However, the result can be falsely high or falsely low in anemia, in inherited hemoglobin disorders (hemoglobinopathies), after a recent transfusion, in chronic kidney disease and in pregnancy. In these situations, HbA1c is interpreted alongside your measured blood glucose values.

Estimated average glucose (eAG) translates HbA1c into a value expressed in the same units as your everyday blood glucose. The formula used internationally is: eAG in mg/dL equals HbA1c in percent multiplied by 28.7, and 46.7 is then subtracted from the result [1]. For example, an HbA1c of 7% (53 mmol/mol) corresponds to an average blood glucose of about 154 mg/dL, or 8.6 mmol/L. This figure is a statistical average derived from large groups of people: in any given individual, the true average blood glucose may be appreciably higher or lower. The calculator above performs this conversion automatically, in both units.

In addition to the percentages traditionally used (the DCCT/NGSP system), HbA1c can also be expressed in mmol/mol, according to the international IFCC standard. The two convert into one another: mmol/mol equals HbA1c in percent minus 2.15, all multiplied by 10.929 [2]. For example, 7% corresponds to 53 mmol/mol, and 6.5% to 48 mmol/mol. Many lab reports now show both values.

For many adults with diabetes, a common target is an HbA1c below 7% (53 mmol/mol), but the right value for you is set individually, together with your doctor. It may be stricter if you are healthy and at low risk of hypoglycemia. It may be more relaxed if you have severe hypoglycemia, other serious illnesses or frail health [3]. The calculator shows which average blood glucose your value corresponds to, but it does not replace a conversation with your medical team.