tuneTypical Dose
1,000–5,000 IU per day
Hormone
Vitamin D
Cholecalciferol (vitamin D3) / Ergocalciferol (vitamin D2)
Evidence TierAWADA NOT PROHIBITED
watchEffect Window
Weeks to months to normalize serum levels.
check_circleCompliance
WADA NOT PROHIBITED
Overview
Clinical Summary
Vitamin D regulates calcium balance, bone mineralization, and immune signaling. It is used to correct low 25(OH)D levels and support bone and muscle function, especially in low sun exposure settings.
Correcting deficiency improves bone mineralization and supports fracture prevention when combined with adequate calcium in older adults. It can improve muscle strength and may reduce falls in some low-status populations. Minority evidence suggests modest effects on respiratory infection outcomes and mood in some trials, but recent guidance and pooled cardiovascular outcome data are more cautious about routine supplementation for broad disease prevention in vitamin D-replete adults. Benefits are strongly dependent on baseline deficiency, and excessive dosing can cause hypercalcemia and related complications.
Pro-hormone that binds the Vitamin D Receptor (VDR), regulating calcium absorption, immune modulation, and gene expression across hundreds of targets.
Outcomes
What This Is Expected To Influence
Primary Outcomes
- Corrects deficiency and raises serum 25(OH)D levels
- Prevents rickets, osteomalacia, and reduces fracture risk in elderly
Secondary Outcomes
- Reduces risk of falls in elderly
- Modest reduction in upper respiratory infection rate
- Improvement in depressive symptoms when correcting deficiency
Safety
Contraindications and Interactions
Contraindications
- Hypercalcemia
- Sarcoidosis (vitamin D hypersensitivity, higher hypercalcemia risk)
- Granulomatous disease (higher hypercalcemia risk)
- Primary hyperparathyroidism
Side effects
- None at physiological doses.
- Hypercalcemia - Risk rises with sustained high intakes (especially >10,000 IU/day) and can progress to hypercalciuria, kidney stones, and soft-tissue calcification.
- Kidney injury - Usually secondary to prolonged hypercalcemia from high-dose intake.
Interactions
- Fish Oil (Possible/Moderate) - The combination of vitamin D and fish oil may raise HbA1c levels by a low but possibly clinically significant amount in people with a vitamin D deficiency.
- Drugs that are CYP3A4 substrates (Possible/Minor) - Vitamin D can induce CYP3A4 enzymes and decrease the levels and effects of CYP3A4 substrates.
- Atorvastatin (Possible/Minor) - A small study showed that vitamin D daily reduced the levels of atorvastatin, a CYP3A4 substrate, but does not seem to clinically affect its cholesterol-lowering ability.
- Strontium (Possible/Unknown) - Long-term (>2 years) use of vitamin D can increase the absorption of strontium, but more research is needed to understand if this interaction could increase the risk of strontium toxicity.
- Supplements that are CYP3A4 substrates (Possible/Unknown) - Vitamin D can induce CYP3A4 enzymes and decrease the levels and effects of CYP3A4 substrates.
- Orlistat (Possible/Moderate) - Can reduce vitamin D absorption.
- Corticosteroids (Possible/Moderate) - Can reduce vitamin D metabolism and blunt response.
- Thiazide diuretics (Possible/Moderate) - Additive risk of hypercalcemia when combined with vitamin D.
Avoid if
- Pregnant or breastfeeding people without clinician-guided dosing and serum 25(OH)D monitoring
- People using fish oil with vitamin D deficiency should monitor HbA1c
- Sarcoidosis
- Granulomatous disease
- Hypercalcemia of any etiology
Evidence
Study-level References
vitamin-d-SRC-001Review / Guideline
Sourceopen_in_newIOM (Institute of Medicine). "Dietary Reference Intakes for Calcium and Vitamin D." 2011.
Population: General Public
Key findings: Establishes role in bone health and sets RDAs.
Paper content
Establishes role in bone health and sets RDAs.
vitamin-d-SRC-002Clinical practice guideline
Sourceopen_in_newVitamin D for the prevention of disease: an Endocrine Society clinical practice guideline. Journal of Clinical Endocrinology and Metabolism. 2024. PMID:38828931.
Population: General population and selected high-risk groups considered by guideline panel.
Dose protocol: Guideline-level review rather than a single supplementation protocol.
Key findings: Updated Endocrine Society guidance emphasizes vitamin D use for deficiency correction and selected high-risk groups rather than routine broad supplementation or screening in healthy adults.
Notes: Guideline framing matters for wording and recommendation boundaries, not just dose selection.
Paper content
Updated guidance emphasizes deficiency correction and selected high-risk use rather than routine broad supplementation or screening in healthy adults.
vitamin-d-SRC-003Systematic review and meta-analysis
Sourceopen_in_newCong B, Zhang H. The effects of combined calcium and vitamin D supplementation on bone mineral density and fracture risk in postmenopausal women with osteoporosis: a systematic review and meta-analysis of randomized controlled trials. BMC Musculoskelet Disord. 2025;26(1):928. doi:10.1186/s12891-025-09089-7. PMID:41063100.
Population: Postmenopausal women with osteoporosis.
Dose protocol: Combined calcium and vitamin D supplementation in postmenopausal osteoporosis studies.
Key findings: Review supports bone-focused benefit framing for vitamin D in high-risk osteoporosis contexts, especially when combined with calcium.
Notes: This is not evidence for universal supplementation in healthy, vitamin D-replete adults.
Paper content
This high-risk-population review supports bone-focused benefit framing for vitamin D when used in context, especially alongside calcium in postmenopausal osteoporosis rather than as a blanket disease-prevention supplement.
vitamin-d-SRC-004Systematic review and pooled meta-analysis of randomized clinical trials
Sourceopen_in_newQudah T, Al-Damook N, Abu Hait K, Abumweis S. Vitamin D supplementation and cardiovascular disease events: a systematic review and pooled meta-analysis of randomized clinical trials. Appl Physiol Nutr Metab. 2026;51:1-13. doi:10.1139/apnm-2025-0158. PMID:41183312.
Population: Adults enrolled in nine randomized placebo-controlled trials evaluating vitamin D and cardiovascular outcomes.
Dose protocol: Varied vitamin D regimens across nine randomized cardiovascular outcome trials.
Key findings: Pooled randomized evidence did not show cardiovascular-event or cardiovascular-mortality reduction with vitamin D supplementation.
Notes: This is mainly a boundary-setting source that helps prevent overclaiming outside deficiency correction and bone-focused use.
Paper content
Large-scale randomized evidence remains neutral for cardiovascular-event prevention with vitamin D supplementation, reinforcing that deficiency correction and bone-focused indications are stronger than broad cardioprotection claims.
vitamin-d-SRC-005Systematic review and meta-analysis.
Sourceopen_in_newBouden S, Ben Messaoud M, Saidane O, et al. Effect of cholecalciferol versus calcifediol on serum 25(OH)D concentrations: a systematic review with meta-analysis. Eur J Clin Nutr. 2025;79(4). doi:10.1038/s41430-024-01520-x. PMID:39385006.
Population: 1,575 participants across 17 studies comparing cholecalciferol and calcifediol.
Dose protocol: Cholecalciferol versus calcifediol across 17 studies with 1,575 participants
Key findings: Calcifediol was more effective than cholecalciferol at raising serum 25(OH)D. 12 of 17 trials favored calcifediol.
Notes: Useful for form selection guidance, particularly in patients with impaired hepatic hydroxylation, obesity, or malabsorption.
Paper content
This meta-analysis of 17 studies with 1,575 participants compared cholecalciferol (standard vitamin D3) with calcifediol (25-hydroxyvitamin D3, the pre-hydroxylated form) for raising serum 25(OH)D levels. Calcifediol was more effective overall, with 12 of 17 trials favoring it over cholecalciferol, 2 showing equivalence, and 3 favoring cholecalciferol. This has practical implications for form selection, particularly in patients with impaired hepatic hydroxylation, obesity (where calcifediol may be less sequestered in adipose tissue), or malabsorption conditions where faster and more reliable 25(OH)D elevation is needed.
vitamin-d-SRC-006Umbrella review and meta-analysis.
Sourceopen_in_newCastro-Luna G, Gomez Galera H, Sanchez Martinez M, et al. Vitamin D status and sepsis outcomes: a PRISMA-compliant umbrella review and meta-analysis. Nutrients. 2026;18(5):869. doi:10.3390/nu18050869. PMID:41830039.
Population: Patients from 19 systematic reviews and over 300 primary studies examining vitamin D and sepsis outcomes in adults and children.
Dose protocol: Umbrella review of 19 systematic reviews and 300+ primary studies on vitamin D and sepsis
Key findings: Vitamin D deficiency consistently associated with increased sepsis susceptibility, severity, and mortality. Supplementation did not show consistent benefit for established sepsis.
Notes: Reinforces deficiency-correction framing. Consistent with the pattern where low status is a risk marker but supplementation in acute illness shows limited benefit.
Paper content
This umbrella review synthesized evidence from 19 systematic reviews and over 300 primary studies on vitamin D and sepsis. Vitamin D deficiency was consistently associated with increased sepsis susceptibility, severity, and mortality across adult and pediatric populations. However, vitamin D supplementation did not show consistent benefit for treating established sepsis. This pattern is consistent with the broader vitamin D literature where deficiency correction is meaningful but supplementation in acute disease states shows limited therapeutic impact. The study reinforces the value of maintaining adequate vitamin D status as a potential risk modifier while cautioning against expecting therapeutic benefit from supplementation once sepsis is established.