Vitamin D3
Commonly used for
EnergyImmunityMuscle & StrengthHeart HealthHealthy AgingFocus
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What is it? / Overview
Wellness uses some people report: antiviral support. This is anecdotal, and there isn't strong clinical evidence that it works for everyone. Vitamin D supports calcium absorption, bone strength, muscle function, and normal immune activity. Many adults have inadequate levels especially with limited sun exposure. Correcting deficiency often improves musculoskeletal health and optimizes long-term wellness.
How is it used? / Administration
Form: Vitamin D3 (cholecalciferol)
Typical dose studied: 1,000–2,000 IU/day maintenance; 2,000–4,000 IU/day for deficiency
Timing: With fat-containing meal, same time daily
D3 preferred over D2. Avoid megadoses unless medically indicated. Pair with adequate calcium when appropriate.
What does it pair with?
Pairs well with:
Adequate magnesium helps the body properly metabolize vitamin D — Magnesium participates in vitamin D metabolism; a randomized trial found magnesium plus D increased blood vitamin D levels more than D alone in overweight/obese adults, though other outcomes weren't consistently improved.
Frequently combined for bone and calcium support, but not required together — Often formulated together, but evidence doesn't establish that everyone taking vitamin D must also take K2.
How well does it work? / Evidence
✓ Well-established
Who should avoid it?
Avoid with: Hypercalcemia; Hyperparathyroidism; Sarcoidosis / Granulomatous disease
Interacts with: Thiazide diuretics; Digoxin; Orlistat may reduce absorption
Already taking it? Check total intake from multivitamins. Recheck levels after 8–12 weeks if treating deficiency.
Research & references
Holick MF. (2011). Evaluation and Treatment of Vitamin D Deficiency. Endocrine Society. Bouillon R et al. (2022). Vitamin D and Human Health. Lancet Diabetes & Endocrinology. Institute of Medicine. (2011). Dietary Reference Intakes for Calcium and Vitamin D.
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