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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.

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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.

How to take it

TimingDosing is weekly, fortnightly or monthly on a schedule set by a doctor, not daily.
With food?With a meal containing fat.
Worth knowingIt raises 25(OH)D within days rather than weeks, so any blood test should be timed by whoever prescribed it or the number will mislead.

Interactions

With medications

  • thiazide diuretics

    Both raise serum calcium, and together they can push it into hypercalcemia. have calcium monitored and do not self-dose

  • digoxin

    Raised calcium increases the risk of digoxin toxicity and arrhythmia. only with medical supervision and calcium monitoring

  • cholestyramine, colestipol and orlistat

    They bind fat and reduce absorption of vitamin D compounds. separate by at least 4 hours

With other supplements

  • vitamin D3 (cholecalciferol)

    Additive, and calcifediol is far more potent per microgram — a fast route to excess. do not take both

  • calcium supplements

    The combination is what actually causes hypercalcemia. keep total calcium modest and have levels checked

Well-established interactions only — this is not a complete list. Always tell your doctor and pharmacist what you take.

Frequently asked questions

Is calcifediol better than vitamin D3?

Calcifediol raises blood 25(OH)D faster and more predictably than vitamin D3: a meta-analysis of 17 studies found it more effective, though not every trial agreed. No trial has shown it prevents fractures, falls or infections better than D3, so any outcome advantage is unproven.

Does calcifediol correct vitamin D deficiency?

Yes: in a trial in 101 young adults with deficiency, 82% reached the target 25(OH)D range within four months on calcifediol, a moderate-grade result. After five more months, 89% stayed above 20 ng/mL versus 49% on placebo.

How is calcifediol dosed?

Calcifediol trials used roughly 266 mcg monthly, or every two weeks in severe deficiency, on a schedule set by a doctor rather than daily. It is a prescription medicine in many countries and far more potent per microgram than vitamin D3.

Can calcifediol cause high calcium?

Yes: because it skips a regulatory step, calcifediol can cause hypercalcemia faster than D3 if overdosed, so levels should be monitored. Do not combine it with vitamin D3, and use it only under supervision with thiazide diuretics or digoxin.

Scientific references

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