vitaminDsubstitution

VitaminDSubstitution refers to the therapeutic replacement of deficient or insufficient vitamin D levels in humans, typically with dietary supplements or fortified foods. The goal is to restore serum 25-hydroxyvitamin D to a physiologic range, usually 20 to 50 ng/mL, thereby supporting bone health, calcium metabolism, and potentially reducing risks of certain chronic diseases.

The most common forms used for substitution are vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). Vitamin D3 is preferred for long‑term therapy because it has a higher conversion rate to 25-hydroxyvitamin D and a longer half‑life. Dosage regimens vary; a typical adult maintenance dose is 800–2 000 IU/day, while high‑dose therapy may involve weekly or monthly administrations of 50 000 IU for correction of severe deficiency.

Indications include osteopenia and osteoporosis, rickets in children, hypocalcemia, and conditions that impair vitamin D absorption such as bariatric surgery or inflammatory bowel disease. Contraindications include hypercalcemia, sarcoidosis, or severe hyperparathyroidism, and caution is required in renal impairment where 1α‑hydroxylation is limited.

Common adverse effects of over‑supplementation are hypercalcemia, polyuria, and, rarely, nephrolithiasis. Monitoring of serum calcium and 25-hydroxyvitamin D is recommended. Randomized trials have shown that vitamin D substitution lowers fracture risk in older adults, though benefits for cardiovascular or cancer outcomes remain inconclusive.