Fat-soluble vitamin
Vitamin D
Also known as calciferol, vitamin D2, and vitamin D3
Vitamin D is a fat-soluble vitamin that helps your body absorb calcium and maintain the calcium and phosphate levels needed for bone mineralization. It occurs naturally in relatively few foods, is added to fortified foods, is available in supplements, and is produced in skin after ultraviolet exposure.
Adult RDA through 70
15 mcg (600 IU)
Adult RDA over 70
20 mcg (800 IU)
FDA Daily Value
20 mcg (800 IU)
Unit conversion
1 mcg = 40 IU
Function
What vitamin D does
Promotes calcium absorption in the gut.
Helps maintain calcium and phosphate concentrations needed for normal bone mineralization.
Supports bone growth and remodeling.
Participates in neuromuscular, immune, inflammatory, and other cellular processes.
Forms
Vitamin D2 and D3 are related, not identical
Vitamin D2
Ergocalciferol
Found in some mushrooms and supplements. It is absorbed and can raise serum 25(OH)D.
Vitamin D3
Cholecalciferol
Produced in skin and found in animal-derived foods and supplements. NIH summarizes evidence that D3 generally raises serum 25(OH)D more and maintains the increase longer than D2.
Daily needs
Vitamin D intake references by age
Infants use an Adequate Intake because evidence was not sufficient to set an RDA. From age 1, the table uses Recommended Dietary Allowances. These values assume minimal sun exposure.
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| Population | Reference | Daily intake |
|---|---|---|
| Birth to 6 months | AI | 10 mcg 400 IU |
| 7 to 12 months | AI | 10 mcg 400 IU |
| 1 to 3 years | RDA | 15 mcg 600 IU |
| 4 to 8 years | RDA | 15 mcg 600 IU |
| 9 to 13 years | RDA | 15 mcg 600 IU |
| 14 to 18 years | RDA | 15 mcg 600 IU |
| 19 to 50 years | RDA | 15 mcg 600 IU |
| 51 to 70 years | RDA | 15 mcg 600 IU |
| Over 70 years | RDA | 20 mcg 800 IU |
| Pregnancy and lactation, ages 14 to 50 | RDA | 15 mcg 600 IU |
FDA label Daily Values are 10 mcg (400 IU) for infants through 12 months, 15 mcg (600 IU) for children ages 1 to 3 and for pregnancy and lactation, and 20 mcg (800 IU) for adults and children age 4 and older. Daily Value is a standardized label reference, not a personalized requirement. Vitamin D labels list mcg per serving and may also show IU in parentheses.
Food sources
Where vitamin D appears in food
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| Food | Serving | Vitamin D | Percent DV |
|---|---|---|---|
| Cod liver oil | 1 tablespoon | 34 mcg 1,360 IU | 170% |
| Rainbow trout, farmed, cooked | 3 ounces | 16.2 mcg 645 IU | 81% |
| Sockeye salmon, cooked | 3 ounces | 14.2 mcg 570 IU | 71% |
| White mushrooms, raw, UV-exposed | 1/2 cup | 9.2 mcg 366 IU | 46% |
| Fortified 2% milk | 1 cup | 2.9 mcg 120 IU | 15% |
| Fortified soy, almond, or oat beverage | 1 cup | 2.5 to 3.6 mcg 100 to 144 IU | 13 to 18% |
| Fortified ready-to-eat cereal | 1 serving | 2 mcg 80 IU | 10% |
| Atlantic sardines, canned in oil | 2 sardines | 1.2 mcg 46 IU | 6% |
| Egg, scrambled | 1 large | 1.1 mcg 44 IU | 6% |
Values are selected from the NIH vitamin D food table, which cites USDA FoodData Central. Fortified products vary by brand, and food amounts can vary by species, preparation, and serving.
Sunlight
Food intake and skin synthesis are different measurements
Skin can synthesize vitamin D when ultraviolet B radiation reaches it.
Season, time of day, day length, cloud cover, skin melanin, clothing, age, and other factors change how much is produced, so a universal minutes-of-sun estimate is not reliable.
UVB does not pass through window glass well enough for sunlight through a closed window to count as equivalent exposure.
Sun-driven synthesis is not dietary intake and cannot be calculated from a food log.
Low status
Who is more likely to have inadequate vitamin D status
Breastfed infants
Older adults
People with limited sun exposure
People with dark skin
People with conditions that limit fat absorption
People with obesity or a history of gastric bypass surgery
Low logged intake does not diagnose vitamin D deficiency. Deficiency can lead to rickets in children and osteomalacia in adolescents and adults, but serum status and clinical context are separate from a food record.
Upper limits
The upper limit is not a daily target
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| Population | Upper limit |
|---|---|
| Birth to 6 months | 25 mcg 1,000 IU |
| 7 to 12 months | 38 mcg 1,500 IU |
| 1 to 3 years | 63 mcg 2,500 IU |
| 4 to 8 years | 75 mcg 3,000 IU |
| Age 9 and older | 100 mcg 4,000 IU |
| Pregnancy and lactation, age 14 and older | 100 mcg 4,000 IU |
The Tolerable Upper Intake Level is a high-intake boundary, not a target. NIH reports that vitamin D toxicity is almost always caused by excessive supplement intake rather than ordinary food intake or sun exposure.
Absorption and interactions
How form, meals, and medications fit in
Absorption
- D2 and D3 are absorbed in the small intestine.
- Fat present in the gut enhances absorption, but some vitamin D is absorbed without dietary fat.
- Vitamin D from sun, foods, and supplements is converted first to 25(OH)D and then to active 1,25-dihydroxyvitamin D.
Medication interactions
- Orlistat can reduce absorption of vitamin D and other fat-soluble vitamins.
- High-dose vitamin D supplements might reduce the effectiveness of some statins.
- Corticosteroids such as prednisone can reduce calcium absorption and impair vitamin D metabolism.
- Thiazide diuretics combined with vitamin D supplements can raise blood calcium too high in some people.
Testing
What a vitamin D blood test measures
Serum 25-hydroxyvitamin D, written 25(OH)D and also called calcidiol, is the main indicator of vitamin D status. It is different from active 1,25-dihydroxyvitamin D, or calcitriol.
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| nmol/L | ng/mL | National Academies framework presented by NIH |
|---|---|---|
| Less than 30 | Less than 12 | Associated with deficiency in the National Academies framework presented by NIH |
| 30 to less than 50 | 12 to less than 20 | Generally considered inadequate for bone and overall health in healthy people |
| 50 or more | 20 or more | Generally considered adequate for bone and overall health in healthy people |
| More than 125 | More than 50 | Linked to potential adverse effects, especially above 150 nmol/L or 60 ng/mL |
NIH notes that serum concentrations associated with deficiency have not been definitively identified. One ng/mL equals 2.5 nmol/L. Lab ranges and organization-specific interpretations can differ.
Tracking
Use food records to review intake, not diagnose status
- 01Record foods and the portions actually eaten.
- 02Use the package label for fortified products because brands vary.
- 03Review repeated intake across several days instead of treating one meal as the whole pattern.
- 04Keep dietary intake separate from supplements, sun-driven skin synthesis, and blood status.
Related nutrients
Vitamin D works inside a larger mineral system
FAQ
Common vitamin D questions
What does vitamin D do?
Vitamin D promotes calcium absorption and helps maintain calcium and phosphate concentrations needed for normal bone mineralization. It also participates in bone remodeling, neuromuscular function, immune function, inflammation, and other cellular processes.
How much vitamin D do adults need?
The RDA is 15 mcg (600 IU) for adults through age 70 and 20 mcg (800 IU) for adults older than 70. The FDA Daily Value is 20 mcg (800 IU), which is a label reference rather than a personalized target.
What is the difference between vitamin D2 and D3?
D2 is ergocalciferol and D3 is cholecalciferol. Both can raise serum 25(OH)D, but NIH summarizes research showing that D3 generally raises it more and maintains the increase longer.
Which foods contain vitamin D?
Fatty fish and fish liver oils are among the richest natural sources. UV-exposed mushrooms, fortified milk or plant beverages, fortified cereal, eggs, and some other animal foods can also contribute.
Can sunlight provide enough vitamin D?
Skin can produce vitamin D after UVB exposure, but production varies with season, time, cloud cover, skin melanin, clothing, age, and other factors. That makes a universal minutes-of-sun estimate unreliable.
What does a vitamin D blood test measure?
The main status test measures serum 25-hydroxyvitamin D, written 25(OH)D. It is not the same as measuring active 1,25-dihydroxyvitamin D.
Is the vitamin D upper limit a target?
No. The UL is a high-intake boundary, not a recommended goal. It varies by age and is especially relevant when total supplement intake becomes high.
Can a food log diagnose vitamin D deficiency?
No. A food log can reveal dietary patterns, but it cannot measure sun-driven synthesis or serum 25(OH)D and cannot diagnose deficiency.
Sources
Primary references
Reviewed July 21, 2026
Put the food pattern in context
Log foods first, then review the pattern across several days.
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