What role does HbA1c play in Sport?

HbA1c (glycated hemoglobin) reflects average blood glucose over the preceding 2–3 months. In sports, it is primarily used to monitor glycemic control in athletes with diabetes or prediabetes. In metabolically healthy athletes, HbA1c may be slightly lower due to enhanced insulin sensitivity and increased glucose uptake by muscles, indicating favorable metabolic adaptation. However, HbA1c is not a direct performance marker. It is influenced by red blood cell turnover, iron deficiency (sports anemia), or blood loss, which can produce falsely low values. It also fails to capture acute glucose fluctuations during exercise. For practical sports monitoring, continuous glucose monitors (CGM) or fasting glucose are often more informative. Direct-to-consumer HbA1c tests exist but require clinical context—training status, diet, and hemoglobin levels—for meaningful interpretation. Conclusion: HbA1c can serve as a metabolic health indicator in athletes but should not replace performance diagnostics. Evidence: human-moderate.