Hemoglobin A1c (HbA1c) tests are highly accurate for reflecting average blood sugar control over the past 2-3 months in most people, as they measure glycated hemoglobin in red blood cells, which tracks cumulative glucose exposure. This makes HbA1c the gold standard for diabetes monitoring and diagnosis, correlating strongly with risks of complications like retinopathy.
Key Strengths
HbA1c captures chronic hyperglycemia better than single glucose tests, shows low day-to-day variability, and requires no fasting, improving clinical convenience. Studies like DCCT confirm that lower HbA1c levels (e.g., ≤7%) reduce microvascular complications by 35-76%.
Limitations and Inaccuracies
Certain conditions cause falsely high or low results: hemolytic anemia or recent blood loss lowers HbA1c, while iron deficiency or uremia raises it; recent glucose changes disproportionately affect readings since recent weeks weigh more heavily. Point-of-care tests may have higher variability or bias compared to lab assays, so confirmation with glucose monitoring or alternatives like fructosamine is advised in mismatches.
Clinical Use Tips
For reliable results, use NGSP-certified labs; a ≥0.5% change is clinically meaningful. In cases like pregnancy or kidney disease, supplement with continuous glucose monitoring or capillary glucose logs to verify control.
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