Evidence check: Vitamin D Test in the context of Sport

The evidence for routine Vitamin D testing in athletes is mixed. Vitamin D is essential for bone health, immune function, and possibly muscle strength. Deficiency can impair performance and recovery. However, the benefit of testing asymptomatic athletes without risk factors (e.g., limited sun exposure, dark skin) is not clearly established. Most guidelines recommend testing only when deficiency is suspected or in high-risk groups. Reference ranges vary, and the correlation between serum levels and athletic performance is weak. Testing may be useful if it leads to targeted supplementation, but overinterpretation of single values should be avoided. Overall, the evidence combines physiological plausibility with limited clinical proof. Direct-to-consumer tests further lack standardization, reducing reliability.