How it came about
In 1968 Iranian-born physician Samuel Rahbar noticed an unusually large hemoglobin fraction in blood from people with diabetes. By 1976 Anthony Cerami's lab had shown that this fraction tracks glucose control over time. Until then, doctors relied on single finger-stick or urine sugar readings that swung wildly from hour to hour. The landmark Diabetes Control and Complications Trial (1993) proved that lowering A1C cuts eye, kidney, and nerve complications, making it the standard treatment target. After labs standardized the assay through the NGSP and IFCC, the American Diabetes Association added it to its diagnostic criteria in 2010.
Reading your number
Because red blood cells live about 120 days, A1C reflects roughly the last two to three months. Below 5.7% is normal, 5.7–6.4% signals prediabetes, and 6.5% or higher on two tests means diabetes. Estimated average glucose (mg/dL) ≈ 28.7 × A1C − 46.7, so 7% works out to about 154 mg/dL. Iron-deficiency anemia can push results up, while blood loss, hemolysis, pregnancy, and chronic kidney disease can pull them down—so doctors pair it with fasting glucose or continuous glucose monitoring.
Bringing it down
Losing 5–7% of body weight and getting at least 150 minutes a week of brisk activity plus strength training sharply lowers the odds that prediabetes becomes diabetes. Cutting refined carbs and sugary drinks and eating fiber-rich vegetables first also helps. Most adults with diabetes aim for under 7%, but older adults or people prone to hypoglycemia may target 7.5–8%. Since the number moves slowly, it's usually rechecked every three months.
This article is general health information and is not a substitute for diagnosis or treatment. If symptoms persist, see a doctor.
FAQ
- Do I need to fast for an A1C test?
- No. It reflects an average, so you can eat beforehand.
- Can I have diabetes with a normal A1C?
- Yes—anemia or kidney disease can skew it low, and early on fasting glucose or a glucose tolerance test may catch it first.
Sources reviewed: 2026-10-26
References
- American Diabetes Association. (2025). Standards of Care in Diabetes—2025: 2. Diagnosis and classification of diabetes. Diabetes Care, 48(Suppl 1).
- Nathan, D. M., et al. (2008). Translating the A1C assay into estimated average glucose values. Diabetes Care, 31(8), 1473–1478.
- 대한당뇨병학회. (2025). 당뇨병 진료지침 제9판.