Definition: HbA1c, or A1C, is a blood test that shows your average blood sugar over the past two to three months. Sugar in the blood sticks to hemoglobin in red blood cells, and the test measures the percentage of hemoglobin coated with sugar. Red blood cells live about three months, which sets the time window.
| Result | Meaning |
|---|---|
| Below 5.7% | Normal |
| 5.7% to 6.4% | Prediabetes |
| 6.5% or above | Diabetes |
MedlinePlus says these ranges are a guide, and that providers often confirm a high result with a second test. The CDC says you do not need to fast for an A1C test.
A1C is the main blood sugar result in the diabetes trials on GLP-1 drug labels. The Ozempic label reports that semaglutide lowered HbA1c compared with placebo in adults with type 2 diabetes, and the Mounjaro label uses HbA1c the same way for tirzepatide. The CDC says most people with diabetes have A1C tested at least twice a year.
The CDC says a home glucose check is a snapshot of one moment, while A1C is a three-month average, so the two answer different questions. A1C does not replace home monitoring.
The CDC lists severe anemia, kidney failure, liver disease, blood disorders such as sickle cell anemia, blood loss or transfusions, early or late pregnancy, and certain medicines including opioids and some HIV drugs. Tell your provider if any apply.
Read more on Dose Track: Blood sugar · Semaglutide guide · Logging lab results in Dose Track