Sickle Cell Trait + Diabetes: Why Your A1C May Not Be Accurate

Beyond Type 1 explains why A1C, one of the most common diabetes monitoring tools, can be misleading for people with sickle cell trait and other hemoglobin variants. A1C estimates average blood glucose over roughly three months by measuring glycated hemoglobin, but that calculation assumes red blood cells and hemoglobin behave in expected ways. In people with sickle cell trait, red blood cells may have a shorter lifespan, giving glucose less time to attach and potentially producing falsely low A1C results.

The article cites a JAMA study finding that sickle cell trait was associated with lower A1C readings relative to actual blood glucose levels. The issue has major equity implications because sickle cell trait affects an estimated 1 to 3 million Americans, including about 8% to 10% of Black Americans, and many people do not know they carry it. If A1C underestimates glucose exposure, clinicians may delay diagnosis, undertreat diabetes, or mistakenly conclude that a person’s management plan is working.

The article also notes that other hemoglobin variants, including hemoglobin C trait, hemoglobin E trait, and elevated fetal hemoglobin, can interfere with A1C accuracy. It recommends comparing lab A1C with daily glucose readings or CGM-derived glucose management indicator, especially when the gap is persistent. Alternatives such as fructosamine and glycated albumin tests can measure shorter-term glycemic exposure without relying on hemoglobin, making them useful when A1C may be unreliable.