Vitamin D3: evidence, dose and safety
Vitamin D3 (cholecalciferol) is the form the skin makes in sunlight. Food holds little of it: oily fish, egg yolk and fortified foods. Our vegan D3 comes from lichen.
At a glance
- Strongest evidence
- A Strong
- Dose in our plans
- 1000 IU a day for adults
- Adult upper limit
- 4000 IU a day from food and supplements together
- Safety checks
- 2 situations and 1 medicine or supplement interaction, checked against your answers in every plan
- Reviewed
- Atrum Labs clinical team (MD, PhD), November 2026
Authorised EU health claim
Vitamin D contributes to the normal function of the immune system.
What the research looked at
Each line is one body of research, graded A (strong) to D (weak). How we grade evidence. What each study measured is explained in your personal plan.
| Grade | Who was studied | References |
|---|---|---|
| A | Adults and children with low 25(OH)D |
|
| A | Infants 0-12 months |
|
| B | Adults 65+ |
|
| B | Adults without a recent vitamin D test |
|
| B | Residents above ~37 degrees latitude |
|
| C | Adults 50+ |
|
| C | Deficient adults |
|
| C | Deficient men |
|
| D | Adults 50+ |
|
| D | Adults |
|
How much
- Our plans usually use 1000 IU a day for adults. The exact dose depends on your lab results, age and medicines.
- Adult upper limit: 4000 IU a day from food and supplements together. Source: EFSA NDA Panel 2023 vitamin D tolerable upper intake level.
- Children's doses are set by age, and some ingredients are for adults only.
Who should not take it, or should check first
- Not suitable. Elevated serum calcium; vitamin D would worsen hypercalcemia.
- Not suitable. 25-hydroxyvitamin D above 125 nmol/L: no benefit from more, and possible harm.
Medicines and other supplements
- A lower dose is used. Thiazides reduce calcium excretion; hypercalcemia risk with high-dose vitamin D.
Your plan is checked against every medicine you tell us about. If you take a medicine, ask your pharmacist or doctor before starting a new supplement.
Products with Vitamin D3
Written and reviewed by the Atrum Labs clinical team (physician-scientists, MD, PhD) from our clinical knowledge base, version 0.2.0-draft. This page is general information, not medical advice. Food supplements are not a substitute for a varied, balanced diet and a healthy lifestyle.
See if it belongs in your plan