Vitamin D
Vitamin D is a fat-soluble vitamin obtained from some foods and supplements and also produced in skin after UVB exposure. It is central to calcium and phosphate metabolism and normal bone mineralization.
What it does in the body
- Promotes intestinal calcium absorption
- Supports normal bone mineralization
- Participates in neuromuscular function
- Has roles in immune function
Daily reference intake
In the U.S. DRI system, 15 µg (600 IU)/day is recommended from age 1 through 70; adults over 70 are recommended 20 µg (800 IU)/day.
What can deficiency look like?
- Deficiency impairs bone mineralization
- In children severe deficiency can cause rickets
- In adults prolonged deficiency can contribute to osteomalacia and bone pain or muscle weakness
Who may be at higher risk?
- Breastfed infants
- Older adults
- People with limited sun exposure
- People with darker skin
- People with fat-malabsorption disorders
- People with obesity or previous gastric-bypass surgery
Food sources
A varied diet is the first place to look for nutrients. Availability and nutrient content can vary by food, preparation and country.
Food-source note: Only a limited number of foods naturally contain substantial vitamin D, so fortified foods can contribute significantly in countries where fortification is common.
Absorption & practical context
Vitamin D is fat soluble and is absorbed with dietary fat. The liver converts vitamin D to 25-hydroxyvitamin D, the form most often measured in blood.
How status is assessed
Serum 25-hydroxyvitamin D [25(OH)D] is the principal laboratory marker used to assess vitamin D status. Interpretation depends on clinical context and laboratory standards.
Important interactions
- Some medicines, including certain steroids and weight-loss medicines, can affect vitamin D metabolism or absorption
- High-dose vitamin D may interact with conditions or medicines that influence calcium levels
Safety and context
Vitamin D toxicity is almost always caused by excessive supplemental intake and can lead to hypercalcemia, kidney injury, soft-tissue calcification and arrhythmias. The adult tolerable upper intake level in the U.S. DRI system is 100 µg (4,000 IU)/day.
Scientific sources
NIH Office of Dietary Supplements — Vitamin D ↗ EU Register of Nutrition and Health Claims ↗Products whose current label lists this nutrient
The entries below are based on current manufacturer label information for the selected market. Compare the stated amount per daily serving and read the official product page before purchasing.