HbA1c
Also called A1c, hemoglobin A1c, glycated hemoglobin, glycohemoglobin
HbA1c (hemoglobin A1c, often shortened to A1c) is a blood test that reflects your average blood glucose over roughly the past two to three months. Glucose in the blood attaches to hemoglobin, the oxygen-carrying protein in red blood cells, and stays attached for the life of the cell, which is about three months. The higher glucose has run, the more hemoglobin carries it, and the test reports that share as a percentage.
Because it averages rather than samples a single moment, A1c is used both to screen for prediabetes and type 2 diabetes and to track diabetes over time, and it does not require fasting. What the result bands mean, and where prediabetes begins, is explained in What A1c Levels Mean, and Where Prediabetes Starts.
Why it matters after 45
The risk of type 2 diabetes rises with age and with weight gain, so A1c becomes a routine part of midlife blood work. It also has blind spots worth knowing. Anything that changes the lifespan of red blood cells, such as recent blood loss, can shift the result, and very low iron can make A1c read falsely high. Some inherited hemoglobin variants, more common in people of African, Mediterranean or Southeast Asian descent, interfere with certain A1c methods. An average also says nothing about swings within the day, which is where fasting insulin or a continuous glucose monitor can add information.
Where it comes up
- CGM vs A1c vs fasting glucosethree different measurements of the same system
- Metformin for prediabetes after 45what the evidence says once A1c reaches the prediabetes range
- Weight gainwhere metabolic testing fits in midlife weight change
- Comprehensive Lab Panelthe baseline panel that includes the metabolic markers
Related terms
References
- MedlinePlus. Hemoglobin A1C (HbA1c) Test. U.S. National Library of Medicine. https://medlineplus.gov/lab-tests/hemoglobin-a1c-hba1c-test/
- National Institute of Diabetes and Digestive and Kidney Diseases. The A1C Test & Diabetes. https://www.niddk.nih.gov/health-information/diagnostic-tests/a1c-test
- National Institute of Diabetes and Digestive and Kidney Diseases. Risk Factors for Type 2 Diabetes. https://www.niddk.nih.gov/health-information/diabetes/overview/risk-factors-type-2-diabetes
Definitions here are educational and are not medical advice. They explain what a term means; the pages linked above cover what it means for you, and a clinician reviews your own results. Editorial & medical review policy · All glossary terms