Vitamin D Supplementation Guidelines for Runners

Dosage Recommendations for Athletes

• Athletes should take 1,000–2,000 IU of vitamin D₃ daily—higher than the 600–800 IU advised for the general population—because their increased physiological demands require higher serum 25(OH)D concentrations. 1

Sun‑Exposure Considerations for Dark‑Skinned Runners

• Dark‑skinned runners need 5–10 times longer sun exposure than light‑skinned runners to generate equivalent vitamin D, reflecting reduced cutaneous synthesis. 2
• When sun exposure is limited (e.g., indoor training, veiled clothing), dark‑skinned or veiled individuals should receive at least 800 IU of vitamin D₃ daily without prior serum testing. [1][2]3

Target Serum Levels and Monitoring

• The optimal serum 25‑hydroxyvitamin D (25(OH)D) range for musculoskeletal health, immune function, and athletic performance in runners is 30–40 ng/mL. [1][3]
• Serum 25(OH)D should be re‑measured after approximately 3 months of supplementation to evaluate response and adjust the dose if needed. [1][2]3
• The upper safety threshold for serum 25(OH)D is 100 ng/mL, providing a wide margin of safety for the recommended dosing regimens. [1][3]

Supplement Formulation

• Vitamin D₂ (ergocalciferol) is not recommended for athletes; vitamin D₃ (cholecalciferol) is more bioavailable and sustains serum levels longer. 4

Calcium Co‑Supplementation

• To support optimal bone health, runners should ensure a total calcium intake of 1,000–1,200 mg per day from diet and/or supplements while using vitamin D. [1][4]