Vitamin D
Helps the body absorb calcium from food.
The formula matches the form shown in the 3D model. Other forms of this vitamin can have different formulas.Loading molecular structure…
Cholecalciferol (D3) · Drag to rotate
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One representative form. Hydrogens omitted; bonds simplified.
PubChem · CID 5280795Where you can find it
- Salmon & trout
- Vitamin D-fortified drinks
- Fortified cereals
- Egg yolks
What it does in the body
Vitamin D supports calcium absorption, bone mineralization and muscle function.
Recommended amounts & upper limit
US reference values for healthy adults aged 19–50, excluding pregnancy and breastfeeding. These are daily dietary intakes, not blood-test ranges or prescribed supplement doses. Other ages and life stages have different needs; see the original source.
- Men · RDA
- 15 mcg (600 IU)/day
- Women · RDA
- 15 mcg (600 IU)/day
- Upper limit · UL
- 100 mcg (4,000 IU)/dayTotal from food, drinks and supplements.
How to read these levels
RDA means Recommended Dietary Allowance; AI means Adequate Intake, used when an RDA cannot be set. The upper limit (UL) is not a target or an exact toxicity threshold. Going below the RDA on one day does not diagnose deficiency. No established UL does not mean unlimited amounts are safe.
mg = milligrams; mcg = micrograms. 1 mg = 1,000 mcg. IU is vitamin-specific and cannot be converted with one rule for all vitamins.
What happens when the balance changes?
These are possible effects, not a diagnosis or a prediction from one low or high result.
Too little
Deficiency can cause rickets in children and osteomalacia in adults, with weak bones and muscle weakness.
Body areas affected
Bones and muscles.
Too much
Excess, usually from supplements, can raise blood calcium, causing nausea, kidney stones and, in severe cases, kidney failure, tissue calcification or abnormal heart rhythms.
Body areas affected
Kidneys, heart and soft tissues.
What about blood-test levels?
Vitamin D status is assessed with serum 25-hydroxyvitamin D, not dietary mcg or IU. Thresholds depend on clinical context and the guideline used.
Blood-test levels and daily intake use different units and cannot be compared directly. Test methods, reference ranges and clinical context vary. Symptoms alone cannot establish a vitamin deficiency or toxicity; a clinician can decide which tests and treatment are appropriate.
The body connection
The intestine absorbs calcium; vitamin D helps make this possible.
Explore small intestine