Supplement analysis backed by scientific evidence · PT

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Moderate evidenceVitamins & minerals

Calcifediol (25-OH Vitamin D)

Vitamin D that has already been hydroxylated once, so it raises blood 25(OH)D faster and more predictably than cholecalciferol. Whether that speed produces any better health outcome has not been tested.

Evidence last reviewed: August 2026

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What the science says

  • Raises blood vitamin D faster than D3 Moderate evidence

    A systematic review with meta-analysis of 17 studies (1575 participants) found calcifediol more effective than cholecalciferol at raising serum 25(OH)D. Twelve trials favoured calcifediol, two found the forms equivalent and three favoured cholecalciferol, so the trials are not unanimous.

  • Corrects and maintains deficiency Moderate evidence

    In a phase I multicentre trial in 101 young adults with vitamin D deficiency, 82% reached the target 25(OH)D range within four months, and after five more months 89% on calcifediol stayed above 20 ng/mL versus 49% on placebo, with no toxic levels observed.

  • No outcome advantage shown Limited evidence

    No trial has shown calcifediol prevents fractures, falls or infections better than ordinary vitamin D3. A 2026 systematic review of 69 trials (153,902 participants) found little to no fracture or fall benefit from vitamin D supplementation at all.

Dosage & safety

Studied doseTrials used roughly 266 µg monthly, or every two weeks in severe deficiency. Calcifediol is a prescription medicine in many countries and is far more potent per microgram than cholecalciferol.
SafetyBecause it skips a regulatory step, calcifediol raises 25(OH)D faster — and so can cause hypercalcemia faster than D3 if overdosed. Levels should be monitored. Avoid in hypercalcemia, sarcoidosis and other granulomatous disease, and use only with medical supervision in advanced kidney disease. Interacts with thiazide diuretics and digoxin.

Scientific references

Where to buy

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