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Vitamin D Dose Calculator

Estimate daily vitamin D3 needed to reach a target serum 25(OH)D level.

Rule of thumb: 100 IU/day raises 25(OH)D ~1 ng/mL; overweight/obese individuals need 1.5–3× more.

Why Target 30–50 ng/mL?

The Endocrine Society defines deficiency as serum 25(OH)D <20 ng/mL, insufficiency as 21–29 ng/mL, and sufficiency at ≥30 ng/mL. Many integrative clinicians target 40–60 ng/mL for optimal immune and bone health. Levels above 100 ng/mL carry a risk of hypercalcemia.

Daily Maintenance Recommendations (Endocrine Society)

  • Adults: 1,500–2,000 IU/day
  • Obese adults: 6,000–10,000 IU/day to maintain levels
  • Children 1–18 y: 600–1,000 IU/day
  • Pregnancy/lactation: 1,500–2,000 IU/day
  • Tolerable Upper Limit: 4,000 IU/day (IOM); 10,000 IU/day (Endocrine Society)

Loading Doses

For documented deficiency, clinicians often use 50,000 IU vitamin D2 or D3 weekly for 8 weeks followed by maintenance dosing.