Is HbA1c useful for Sport?

HbA1c is a long-term blood glucose marker reflecting average glucose levels over the past 2–3 months. For athletes without diabetes, HbA1c is not a direct performance indicator but may offer insights into metabolic health. A lower HbA1c (e.g., <5.5%) is often associated with better insulin sensitivity and glycemic control, which could be relevant for endurance athletes. However, strong evidence that lowering HbA1c improves athletic performance is lacking. HbA1c is influenced by factors such as red blood cell turnover, hemoglobin variants, and training intensity. Intense training can artificially lower HbA1c due to increased erythrocyte turnover, complicating interpretation. For athletes with diabetes, HbA1c is a well-established monitoring tool, but for healthy athletes aiming to optimize performance, it is not recommended as a primary metric. The evidence is moderate, based on observational studies rather than randomized controlled trials. In summary, HbA1c can be useful as a general health marker but not as a specific sport performance indicator. Caution is advised against overinterpreting single values.