VitaminNo.011
Vitamin D3
Bone health, calcium absorption, immune function.
Typical / RDA600–800 IU
Upper limit4,000 IU
EvidenceStrong
How to take it
Timing With breakfastFood With fatForm D3 (cholecalciferol)
What to know
Fat-soluble — take with a meal containing fat. Deficiency is common in indoor workers, darker skin, and limited sun. Strong evidence for correcting measured deficiency.
Interactions & cautions
- Works with magnesium (activation cofactor) and vitamin K2.
- Excess over long periods raises blood calcium — stay under the UL.
Often worth it
Indoor worker or rarely eat oily fish? A likely candidate.
Reference values: NIH Office of Dietary Supplements, adult general population. Educational information only — not medical advice. Confirm with a healthcare professional.