Vitamin D3
5000 IU · Daily
Robert
Founder, F*CK Getting Old — independent researcher, not a medical professional.
Last reviewed · 2 cited sources
Evidence
- Human Studies
- 200
- Animal Studies
- 80
- Clinical Status
- Dietary Supplement
- Confidence
- High
- Long-Term Safety
- Well-established at standard doses; toxicity is rare but possible with chronic high-dose use without monitoring
What this score is: a measure of how much research exists and how far along it is (animal-only vs. human trials, research-stage vs. FDA approved) — not how safe, effective, or worth trying a compound is. A low score usually means “early stage” or “understudied,” not “bad.” A high score doesn’t mean “better” for your goals than a lower-scored one.
This is not my personal rating of the compound, not a recommendation, and not medical advice. It’s a general research synthesis for informational purposes only, not a live literature count. See the linked research and talk to a licensed clinician before making decisions based on it.
Mechanism
A fat-soluble vitamin/prohormone essential for calcium absorption and bone mineralization, with receptors throughout the body implicated in immune and muscle function. Evidence is strongest for correcting deficiency and bone health; large trials (e.g. VITAL) found more modest or null effects on other outcomes in people who weren’t deficient to begin with.
Common Protocols
- 1000–5000 IU daily depending on baseline levels — testing blood 25-OH-D levels before/during supplementation is the most reliable way to dose
- Take with a fat-containing meal for better absorption
Side Effects
- Rare at standard doses
Interactions
- Increases calcium absorption — caution combining with calcium supplements if you have a history of kidney stones
Practical Details
- Cost
- $
- Typical Dose
- 5000 IU
- Storage
- Store in a cool, dry place, away from light
Key Studies & Reviews
- Manson JE et al. (2019). Vitamin D supplements and prevention of cancer and cardiovascular disease (VITAL). N Engl J Med. PMID 30415629.
- LeBoff MS et al. (2022). Supplemental vitamin D and incident fractures in midlife and older adults. N Engl J Med. PMID 35939577.
Search the Research
Vitamin D3 FAQ
What is the typical Vitamin D3 dosage?
Commonly reported protocols: 1000–5000 IU daily depending on baseline levels — testing blood 25-OH-D levels before/during supplementation is the most reliable way to dose; Take with a fat-containing meal for better absorption. Our reference entry uses 5000 IU, Daily. These reflect protocols reported in research and user communities, not a medical recommendation — dosing should be decided with a clinician.
What are the side effects of Vitamin D3?
Reported side effects include: Rare at standard doses.
Is Vitamin D3 FDA approved?
Vitamin D3 is sold as a dietary supplement. The FDA does not approve supplements for safety or effectiveness before they are sold, so third-party tested brands are worth seeking out.
How much research is there on Vitamin D3?
Our evidence profile counts roughly 200 human and 80 animal studies, with high overall confidence. Long-term safety: Well-established at standard doses; toxicity is rare but possible with chronic high-dose use without monitoring.
Does Vitamin D3 interact with other drugs or supplements?
Increases calcium absorption — caution combining with calcium supplements if you have a history of kidney stones.
Related compounds
Bone and immune support; take with a fat-containing meal