Source: NIH Office of Dietary Supplements — Vitamin D — RDA 600–800 IU; 1,000–2,000 IU/day is a common maintenance dose for adults with low sun exposure.
A fat-soluble vitamin that acts more like a hormone, made in your skin from sunlight.
Regulates calcium metabolism and influences hundreds of genes tied to immunity and cell function.
Supplementation raised blood 25(OH)D to sufficiency but did NOT significantly improve muscle strength in athletes who were already replete.
Meta-analysis of 10 RCTs · n=354 · varied — Zhang et al., 2024 — Front. Nutrition (meta-analysis)
Fracture and fall risk depended heavily on dose and dosing interval; daily moderate dosing outperformed infrequent megadoses.
Meta-analysis of RCTs · n=~50,000 · 400–2,000 IU/day — Yao et al., 2019 — JAMA Netw Open (meta-analysis)
Bottom line: Clearly worth it to correct a deficiency — which is common with indoor lifestyles and winter — but topping up when your blood level is already sufficient does little for strength or longevity. The honest move is a blood test, not a guess.
Safe at normal doses. Toxicity (high blood calcium) only occurs from very high chronic intake — get a blood level if dosing above 4,000 IU long-term.
Anecdotes, not evidence, and not medical advice. Frequency labels are our read of forum sentiment, not a formal survey. Individual responses vary widely.
| Per serving | |
|---|---|
| Typical branded single-ingredient product | $0.22 |
| Bulk powder at the clinical dose (500 softgels 5000IU, $20.97) | $0.04 |
Buying bulk powder instead of a branded bottle saves about 81% per serving.
Bulk price: $20.97/500 softgels → Alt source: $9.99/25gEducational only — not medical advice. Grades and clinical doses are computed from public labels against sourced research (citations on the main site); prices last verified 2026-07-21. Expensive Powder has no sponsors; bulk links may earn an affiliate commission, which never affects a grade. Talk to a clinician before starting any supplement.