Rankings / Essentials — Vitamins & Minerals
Vitamin D
Essentials · Vitamin
Also known as: Cholecalciferol ·Vitamin D3 ·25-OH-D
Tier B
Bottom line
Read Off Label grades Vitamin D as B (6.6/10) based on moderate evidence, low benefit magnitude, and a low-risk safety profile.
VITAL (n=25,871) did not find lower incidence of invasive cancer or major cardiovascular events from vitamin D supplementation in generally sufficient US adults.
Studied, labeled, or reported-use context: RDA: 600 IU/day for adults 19-70 and 800 IU/day over 70; adult tolerable upper intake is 4,000 IU/day… — OTC; not individualized guidance.
If you were testing this on yourself
Two properties decide whether an n-of-1 experiment is readable and recoverable. These describe the experiment — they are not a judgment about whether to run it, and nothing here is a recommendation.
Can you undo it?
Slow to reverse
The long half-life means levels take weeks to months to fall after stopping. Toxicity from sustained high dosing causes hypercalcaemia that resolves slowly.
Can you tell if it worked?
Readable — 8–12 weeks to a new steady state
Serum 25-OH-D on a standard blood panel — one of the few things here with a direct, cheap, unambiguous measurement.
What would fool you Sun exposure and season move levels substantially; testing in different seasons compares two different things. A level rising says the supplement is absorbed, not that you feel any different.
What the evidence says
VITAL (n=25,871) did not find lower incidence of invasive cancer or major cardiovascular events from vitamin D supplementation in generally sufficient US adults. Respiratory-infection meta-analyses suggest at most a small, context-dependent benefit. NIH considers 25-OH-D of 20 ng/mL or more sufficient for most people; levels above 50 ng/mL can be associated with adverse effects. The 2024 Endocrine Society guideline does not recommend routine testing or empiric high-dose supplementation for most healthy adults.
Mechanism
Vitamin D from skin synthesis, food, or supplements is converted to 25-hydroxyvitamin D and then the active hormone; it regulates calcium and phosphate balance and supports bone mineralization
Studied, labeled, or reported dose & route
RDA: 600 IU/day for adults 19-70 and 800 IU/day over 70; adult tolerable upper intake is 4,000 IU/day from all sources unless a clinician directs treatment. There is no universal prevention target for 25-OH-D.
This records doses and routes described in studies, approved labeling, clinical practice, or documented use. It is not individualized guidance and does not establish safety; context changes with indication, formulation, health history, monitoring, and other medicines.
Citations
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Common questions
- What does the evidence show about Vitamin D's effects?
- Read Off Label rates the evidence for Vitamin D as Moderate and the benefit magnitude as low, producing an overall grade of B (6.6/10). VITAL (n=25,871) did not find lower incidence of invasive cancer or major cardiovascular events from vitamin D supplementation in generally sufficient US adults.
- What safety findings are reported for Vitamin D?
- Vitamin D has a low risk profile in the database. Low (usual intake); excess can cause hypercalcemia, kidney injury, and other toxicity Legal status: OTC.
- What doses or routes are reported for Vitamin D?
- RDA: 600 IU/day for adults 19-70 and 800 IU/day over 70; adult tolerable upper intake is 4,000 IU/day from all sources unless a clinician directs treatment. There is no universal prevention target for 25-OH-D. This is context from studies, approved labeling, clinical practice, or documented use; it is not individualized guidance and does not establish safety.
- How does Vitamin D work?
- Vitamin D from skin synthesis, food, or supplements is converted to 25-hydroxyvitamin D and then the active hormone; it regulates calcium and phosphate balance and supports bone mineralization
This is an independent synthesis of published research by a non-clinician. Scores are opinions supported by citations, not prescriptions. See the full disclaimer and methodology for how this score was produced and what it does and doesn't mean.