Most adults need 600 IU (15 mcg) of vitamin D per day. Adults over 70 need 800 IU (20 mcg), and infants need 400 IU (10 mcg). Those are the official recommended amounts, but your actual needs can vary quite a bit depending on your weight, skin tone, where you live, and how much sun you get.
Recommended Daily Amounts by Age
The NIH sets these daily intake targets:
- Infants (0–12 months): 400 IU (10 mcg)
- Children and teens (1–18 years): 600 IU (15 mcg)
- Adults (19–70 years): 600 IU (15 mcg)
- Adults over 70: 800 IU (20 mcg)
- Pregnant or breastfeeding women: 600 IU (15 mcg)
These numbers are designed to meet the needs of about 97.5% of healthy people in each group. They assume you’re getting minimal sun exposure, so they represent what you’d need from food and supplements alone.
What the 2024 Endocrine Society Guidelines Changed
The Endocrine Society updated its vitamin D guidelines in 2024, and the recommendations are more nuanced than a single number. For healthy adults under 75, the society actually recommends against taking extra vitamin D beyond the standard 600–800 IU from the NIH guidelines. The evidence didn’t show meaningful benefits from higher doses in this group.
Three groups got different advice. Adults 75 and older should take vitamin D supplements because of a potential reduction in mortality risk. The clinical trials that showed this benefit used doses averaging around 900 IU per day. Children and adolescents benefit from supplementation to prevent rickets and possibly reduce respiratory infections, with study doses averaging about 1,200 IU daily. Pregnant women should supplement as well, given evidence of lower risk for preeclampsia, preterm birth, and other complications.
The guidelines also recommend against routine blood testing for vitamin D levels in the general population, regardless of age. Testing makes sense when a doctor suspects a deficiency based on symptoms or risk factors, but screening everyone hasn’t proven useful.
Why Body Weight Changes Your Needs
If you carry extra weight, the standard 600 IU may not be enough. Vitamin D is fat-soluble, meaning it gets stored in body fat rather than circulating freely in your blood. The more body fat you have, the more vitamin D gets “locked away” where your body can’t use it efficiently.
Research published in PLOS ONE found that overweight individuals need roughly 1.5 times the standard dose to reach the same blood levels as normal-weight people. For those with obesity, the multiplier jumps to 2 to 3 times. In concrete terms, a normal-weight person might need about 2,000 IU daily to reach optimal blood levels, while someone with obesity would need closer to 5,000 IU to hit the same target. BMI turns out to be a better predictor of how much vitamin D you need than body weight alone.
How Sun Exposure Factors In
Your skin produces vitamin D when exposed to UVB rays from sunlight, and for many people this is their primary source. Exposing your bare arms and legs to midday sun (between 10 a.m. and 3 p.m.) for 5 to 30 minutes twice a week can be enough to meet your needs, depending on several factors.
Skin tone makes a significant difference. Melanin, the pigment that gives skin its color, competes with the molecule your skin uses to make vitamin D. People with darker skin may need up to ten times longer in the sun to produce the same amount of vitamin D as someone with fair skin. If you have very dark skin and spend most of your time indoors, supplementation becomes more important.
Where you live matters just as much. If you’re north of about 40 degrees latitude (think Boston, Madrid, or Beijing), your skin can’t produce meaningful vitamin D from roughly November through early March because the sun sits too low in the sky. Ten degrees farther north, around Edmonton or London, that “vitamin D winter” stretches from October to April. During those months, you rely entirely on food and supplements.
What Happens if You Get Too Little
Vitamin D helps your body absorb calcium and maintain strong bones. Without enough, children can develop rickets, a condition where bones become soft and bend. In adults, deficiency leads to a similar condition called osteomalacia, which causes bone pain, muscle weakness, and an increased risk of fractures. Blood levels below 20 ng/mL (50 nmol/L) are generally considered deficient, while levels between 20 and 30 ng/mL are often classified as insufficient.
Beyond bone health, low vitamin D has been linked to a higher risk of respiratory infections, especially in children. The 2024 Endocrine Society review found enough evidence to recommend supplementation for kids partly on this basis.
How Much Is Too Much
You can’t overdose on vitamin D from sunlight or food alone. Toxicity comes from supplements. The safe upper limit is 4,000 IU per day for anyone over age 9. For younger children, the ceiling is lower: 1,000 IU for infants up to 6 months, 1,500 IU for infants 7–12 months, 2,500 IU for ages 1–3, and 3,000 IU for ages 4–8.
The main danger of taking too much vitamin D is a buildup of calcium in the blood. This can cause nausea, vomiting, weakness, frequent urination, bone pain, and kidney stones. Toxicity typically develops from taking very high doses (well above 10,000 IU daily) over extended periods, not from occasionally exceeding the recommended amount.
Food Sources Worth Knowing
Few foods naturally contain much vitamin D. Fatty fish like salmon, mackerel, and sardines are the best natural sources, providing roughly 400–600 IU per 3-ounce serving. Cod liver oil packs even more, about 1,360 IU per tablespoon. Egg yolks contain a small amount, around 40 IU each.
Most of the vitamin D in the American diet comes from fortified foods. A cup of fortified milk or plant-based milk alternative typically provides about 100–120 IU. Fortified cereals and orange juice offer similar amounts. If you’re trying to hit 600 IU from food alone without eating fish regularly, it’s difficult, which is why supplements are so common.
Vitamin D3 (the form your skin makes from sunlight) is generally more effective at raising blood levels than D2 (the plant-derived form). If you’re choosing a supplement, D3 is the better option for most people.