Vitamin D Test: which supplements make sense?

A vitamin D test can help identify deficiency, especially in at-risk groups (elderly, dark skin, limited sun exposure). If deficient, supplementation with vitamin D3 (cholecalciferol) is generally more effective than D2 (ergocalciferol). However, evidence for routine testing in healthy adults is moderate – major guidelines (e.g., USPSTF) do not recommend universal screening due to unclear benefit. Over-supplementation can cause hypercalcemia. Therefore, test only if deficiency is suspected, then supplement accordingly. Genetic factors (e.g., VDR SNPs) have minor influence; lifestyle and sun exposure are key.