How much vitamin D should I take a day?

The recommended dietary allowance for adults is 600 IU (15 mcg) per day from ages 1 to 70, and 800 IU (20 mcg) per day at 71 and older, according to the NIH Office of Dietary Supplements. These are general reference intakes from food and supplements combined. A dose to correct a diagnosed deficiency is individualized and should be set with a clinician.

Can you get too much vitamin D?

Yes, from supplements. The tolerable upper intake level for adults is 4,000 IU (100 mcg) per day, per the NIH Office of Dietary Supplements. Very high supplement doses over time can raise blood calcium to harmful levels. Toxicity does not come from sun exposure, because the skin limits how much vitamin D it makes.

Do I need a vitamin D test?

For most healthy adults without symptoms, routine screening is not recommended. The US Preventive Services Task Force found the evidence insufficient to assess the benefits and harms of screening asymptomatic adults, and no national organization recommends population-wide testing. Whether to test is a clinical decision based on a person's situation.

What foods have vitamin D?

Few foods are naturally rich in it. The main natural sources are oily fish such as salmon and trout, cod liver oil, egg yolks, and mushrooms exposed to UV light. Most dietary vitamin D comes from fortified foods, where it is added during processing, such as milk, many plant milks, and breakfast cereals.

Who is most likely to be deficient in vitamin D?

Groups more likely to fall short include people with little sun exposure, people with darker skin, older adults, breastfed infants, people with conditions that limit fat absorption such as Crohn's or celiac disease, and people with obesity or who have had gastric bypass surgery, per the NIH Office of Dietary Supplements. These are general risk categories, not a diagnosis.

Is vitamin D3 better than D2?

Both forms are well absorbed and raise blood vitamin D levels. The two differ only in a side-chain structure, and some evidence suggests D3 (cholecalciferol) raises levels somewhat more than D2 (ergocalciferol). For most people the practical difference is small, and either form counts toward intake.

Nutrition

Vitamin D: How Much Do Adults Need, and Who Is at Risk?

Vitamin D helps the body absorb calcium and keep bones healthy. This guide covers how much adults need (the NIH recommended intake), where it comes from, who tends to fall short, the safe upper limit, and why routine testing is not recommended for most healthy adults.

Written by Michael Harley, Independent Health & Nutrition ResearcherLast reviewed: Jun 7, 2026

Vitamin D is a fat-soluble vitamin that the body can make on its own. When ultraviolet B rays from sunlight reach the skin, they trigger vitamin D synthesis, which is why it is often called the sunshine vitamin. Its best-established job is helping the body absorb calcium and keep the skeleton healthy. Long-term shortfall is linked to weak bones: rickets in children and osteomalacia in adults, and, together with low calcium, a higher risk of osteoporosis in older adults.

This guide explains how much vitamin D most adults need, where it comes from, who tends to fall short, whether it is possible to take too much, and why routine blood testing is not recommended for most healthy adults. It is general and educational, not personal medical advice.

The essentials at a glance

The recommended dietary allowance for adults is 600 IU (15 mcg) a day from ages 1 to 70, rising to 800 IU (20 mcg) at 71 and older (NIH Office of Dietary Supplements).
Vitamin D is measured in both micrograms and international units: 1 mcg equals 40 IU (NIH ODS).
It comes from sunlight on the skin, a few foods (oily fish, cod liver oil, egg yolks, UV-exposed mushrooms), fortified foods such as milk and cereal, and supplements (NIH ODS).
People more likely to fall short include those with little sun exposure, darker skin, older adults, people with conditions that limit fat absorption, and people with obesity (NIH ODS).
The tolerable upper intake level for adults is 4,000 IU (100 mcg) a day; toxicity comes from high-dose supplements, not from the sun (NIH ODS).
Routine vitamin D screening of healthy adults without symptoms is not generally recommended; whether to test is a decision for a clinician (US Preventive Services Task Force).

How much vitamin D do adults need

The reference intakes most often used come from the NIH Office of Dietary Supplements, based on the Food and Nutrition Board at the National Academies. The recommended dietary allowance for adults is 600 IU (15 mcg) per day from ages 1 through 70, and 800 IU (20 mcg) per day from age 71 onward. The same 600 IU figure applies during pregnancy and breastfeeding.

Vitamin D is reported in two units that often appear side by side. One microgram equals 40 international units, so 15 mcg is 600 IU and 20 mcg is 800 IU. These figures are population reference intakes, meaning amounts intended to meet the needs of nearly all healthy people. They are not a personal prescription, and the Food and Nutrition Board set them assuming minimal sun exposure.

Where vitamin D comes from

There are three broad sources. The first is sunlight: UVB rays striking the skin start vitamin D production, although how much is made depends on season, time of day, latitude, cloud cover, skin pigmentation, and sunscreen use. Because ultraviolet radiation also raises skin-cancer risk, health authorities advise sun protection rather than deliberate tanning to raise vitamin D.

The second source is food, and naturally rich options are few. Oily fish such as salmon and trout, cod liver oil, egg yolks, and mushrooms exposed to UV light contain meaningful amounts. Many staple foods are fortified, meaning vitamin D is added during processing, which is how most people get it from their diet: examples include cow's milk, many plant milks, and breakfast cereals.

The third source is supplements. These come in two forms, D2 (ergocalciferol) and D3 (cholecalciferol), which differ only in a side-chain structure. Both are well absorbed and raise blood levels, and there is some evidence that D3 raises levels somewhat more than D2. Vitamin D is one of the few supplements with a clear, mainstream use case for people who fall short; for another well-evidenced example, the creatine-monohydrate-guide covers a supplement with strong support for exercise and muscle.

Deficiency and who is at risk

Certain groups are more likely than others to have low vitamin D status. These include breastfed infants, older adults, people who get little sun exposure (for example those who are mostly indoors or who cover most of their skin), and people with darker skin, since more melanin reduces how much vitamin D the skin makes from sunlight. People with conditions that limit fat absorption, such as Crohn's disease, celiac disease, or ulcerative colitis, and people with obesity or who have had gastric bypass surgery, are also more prone to shortfall.

These are general categories, not a diagnosis. Belonging to one does not mean a person is deficient, and not belonging to any does not rule it out. Anyone concerned about their own status should raise it with a clinician rather than assume.

Can you take too much?

Yes. Vitamin D is fat-soluble and can build up, so there is a ceiling. The tolerable upper intake level set by the Food and Nutrition Board is 4,000 IU (100 mcg) per day for adults, including older adults and during pregnancy. This is the highest routine daily intake unlikely to cause harm in the general population, not a target to aim for.

Importantly, vitamin D toxicity comes almost entirely from high-dose supplements, not from the sun. Experts do not consider excessive sun exposure a cause of vitamin D toxicity, because the skin limits how much it makes. Taking very large supplement doses over time can raise blood calcium to harmful levels, a state called hypercalcemia, which in serious cases can damage the kidneys and heart. This is why megadosing without medical supervision is not advised.

The testing caveat

It is common to assume that everyone should have their vitamin D level checked, but that is not what major guidelines recommend. In its 2021 statement, the US Preventive Services Task Force concluded that the evidence is insufficient to weigh the benefits and harms of screening for vitamin D deficiency in asymptomatic adults, a finding consistent with its earlier 2014 statement. The NIH Office of Dietary Supplements notes that no national professional organization recommends population-wide screening, and the 2024 Endocrine Society guideline likewise does not recommend routine 25-hydroxyvitamin D testing in healthy people.

Part of the reason is that experts have not agreed on the exact blood level that defines deficiency. Testing still has a role when a clinician suspects a problem or when someone has a relevant condition, but that is a clinical judgment made case by case, not a routine step for healthy adults. Whether to test, and whether to supplement and at what dose, are decisions to make with a clinician.

Frequently asked questions

How much vitamin D should I take a day?: The recommended dietary allowance for adults is 600 IU (15 mcg) per day from ages 1 to 70, and 800 IU (20 mcg) per day at 71 and older, according to the NIH Office of Dietary Supplements. These are general reference intakes from food and supplements combined. A dose to correct a diagnosed deficiency is individualized and should be set with a clinician.
Can you get too much vitamin D?: Yes, from supplements. The tolerable upper intake level for adults is 4,000 IU (100 mcg) per day, per the NIH Office of Dietary Supplements. Very high supplement doses over time can raise blood calcium to harmful levels. Toxicity does not come from sun exposure, because the skin limits how much vitamin D it makes.
Do I need a vitamin D test?: For most healthy adults without symptoms, routine screening is not recommended. The US Preventive Services Task Force found the evidence insufficient to assess the benefits and harms of screening asymptomatic adults, and no national organization recommends population-wide testing. Whether to test is a clinical decision based on a person's situation.
What foods have vitamin D?: Few foods are naturally rich in it. The main natural sources are oily fish such as salmon and trout, cod liver oil, egg yolks, and mushrooms exposed to UV light. Most dietary vitamin D comes from fortified foods, where it is added during processing, such as milk, many plant milks, and breakfast cereals.
Who is most likely to be deficient in vitamin D?: Groups more likely to fall short include people with little sun exposure, people with darker skin, older adults, breastfed infants, people with conditions that limit fat absorption such as Crohn's or celiac disease, and people with obesity or who have had gastric bypass surgery, per the NIH Office of Dietary Supplements. These are general risk categories, not a diagnosis.
Is vitamin D3 better than D2?: Both forms are well absorbed and raise blood vitamin D levels. The two differ only in a side-chain structure, and some evidence suggests D3 (cholecalciferol) raises levels somewhat more than D2 (ergocalciferol). For most people the practical difference is small, and either form counts toward intake.

References

Vitamin D: Fact Sheet for Health Professionals (RDA, tolerable upper intake level, unit conversion, sources, groups at risk, status assessment) · National Institutes of Health, Office of Dietary Supplements. Accessed 2026-06-07.
Vitamin D Deficiency in Adults: Screening (Final Recommendation Statement, April 13, 2021, Grade I) · U.S. Preventive Services Task Force. Accessed 2026-06-07.
Calcium and Vitamin D: Important for Bone Health · National Institutes of Health, National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS). Accessed 2026-06-07.
Vitamin D (consumer health topic) · MedlinePlus, National Library of Medicine (NIH). Accessed 2026-06-07.