Written by Adda Bjarnadottir, MS, RDN (Ice) — Medically reviewed by Kim Chin, RD, Nutrition — Updated on February 19, 2021
Vitamin D is essential for good health.
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It’s often referred to as the “sunshine vitamin” and is made in your skin when exposed to sunlight.
Despite that, vitamin D deficiency is one of the most common nutrient deficiencies in the world.
Up to 42% of the American adult population has low vitamin D levels, which can cause health problems (1, 2, 3, 4, 5).
Vitamin D is crucial for bone health and immune system function.
This article discusses how much vitamin D you need.
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Vitamin D is a fat-soluble vitamin that’s involved in many essential body functions.
There are two forms of vitamin D in the diet and supplements:
Vitamin D2 (ergocalciferol): found in some mushrooms.Vitamin D3 (cholecalciferol): found in oily fish, fish liver oil, and egg yolks.
D3 is the more powerful of the two types and raises vitamin D levels almost twice as much as D2 (6, 7).
Significant amounts of vitamin D can also be made in your skin when exposed to UV rays from sunlight. Any excess vitamin D is stored in your body fat for later use.
Almost every cell in your body has a receptor for vitamin D. It’s essential to many processes, including bone health, immune system function, and can help protect against cancer (8, 9, 10, 11).
Supplements 101: Vitamin D
Vitamin D is involved in many of your body’s functions. There are two forms in the diet, D2 and D3. It can also be produced in your skin when exposed to sunlight.
How common is vitamin D deficiency?
Vitamin D deficiency is a problem all over the world.
However, it’s pervasive in young women, infants, older adults, and people who have dark skin (12, 13, 14).
About 42% of the U.S. population is vitamin D deficient. However, this rate rises to 82% in Black people and 70% in Hispanics, which systemic problems likely play a role in (5).
If you have access to strong sun all year, then occasional sun exposure may be enough to fulfill your vitamin D requirements.
However, if you live far north or south of the equator, your vitamin D levels may fluctuate depending on the season. The levels may go down during the winter months due to a lack of sufficient sunlight (15, 16).
In that case, you may need to rely on your diet (or supplements) for vitamin D as well as on vitamin D that’s stored in body fat (15).
In adults, a vitamin D deficiency may (17, 18, 19):
cause muscle weaknessintensify bone lossincrease the risk of fractures
In children, a severe vitamin D deficiency can cause delays in growth and rickets, a disease where the bones become soft.
Furthermore, vitamin D deficiency is linked with several cancers, type 1 diabetes, multiple sclerosis, high blood pressure, and thyroid problems (17, 20, 21).
Vitamin D deficiency is prevalent worldwide but occurs at higher rates in specific populations. A deficiency in vitamin D is linked to various health problems.
How much vitamin D should you take?
How much vitamin D you need depends on many factors. These include:
age ethnicity latitudeseason sun exposure clothing
This is only a partial list of factors that help determine the amount of vitamin D a person needs.
The National Institutes of Health (NIH) recommends an average daily intake of 400–800 IU, or 10–20 micrograms (22, 23).
However, some studies find that the daily intake needs to be higher if you aren’t being exposed to the sun or have darker skin tones.
Depending on who you ask, blood levels above 20 ng/ml or 30 ng/ml are considered as “sufficient.”
One study involving healthy adults showed that a daily intake of 1,120–1,680 IU was needed to maintain sufficient blood levels (23, 24).
In the same study, individuals who were vitamin D deficient needed 5,000 IU to reach blood levels above 30 ng/ml.
Studies in postmenopausal women with vitamin D levels below 20 ng/ml found that ingesting 800–2,000 IU raised blood levels above 20 ng/ml. However, higher doses were needed to reach 30 ng/ml (25, 26).
People who are overweight or have obesity may also need higher amounts of vitamin D (27, 28).
All things considered, a daily vitamin D intake of 1,000–4,000 IU, or 25–100 micrograms, should be enough to ensure optimal blood levels in most people.
According to the National Institutes of Health, the safe upper limit is 4,000 IU. Make sure not to take more than that without consulting with a healthcare professional (22).
Vitamin D recommended intake is at 400–800 IU/day or 10–20 micrograms. However, some studies suggest that a higher daily intake of 1,000–4,000 IU (25–100 micrograms) is needed to maintain optimal blood levels.
Blood levels of vitamin D are assessed by measuring 25(OH)D in the blood, which is the storage form of vitamin D in the body (28).
However, there’s been some debate over the definition of optimal blood levels.
The Institute of Medicine (IOM) and the Nordic Nutrition Council base their recommendations on the following blood levels (18, 22):
sufficient: 25(OH)D greater than 20 ng/ml (50 nmol/l)insufficient: 25(OH)D less than 20 ng/ml (50 nmol/l)deficient: 25(OH)D less than 12 ng/ml (25 nmol/l)
These organizations claim that blood levels of over 20 ng/ml meet the vitamin D requirements of more than 97.5% of the population.
A committee at the IOM did not find higher blood levels to be associated with any additional health benefits (22).
However, other experts, including the Endocrine Society, recommend aiming for higher blood levels that are closer to 30 ng/ml (75 nmol/l) (17, 29, 30, 31).
Vitamin D levels are generally considered sufficient when above 20 ng/ml (50 nmol/l). However, some experts claim that blood levels above 30 ng/ml (75 nmol/l) are optimal.
You can get vitamin D from:
sun exposurefoods that contain vitamin Dsupplements
Vitamin D intake is generally quite low, since very few foods contain significant amounts (32).
Foods that do contain vitamin D include fatty fish like salmon as well as fish liver oils.
Egg yolks also contain small amounts, and in some countries milk and cereals are enriched with vitamin D (33).
However, supplements are also widely available and are both safe and effective.
The main sources of vitamin D are sunshine, fatty fish, egg yolks, fish liver oils, fortified foods, and supplements.
Summer sun exposure is the most effective way to get enough vitamin D, but it doesn’t come without risk. Additionally, the amount of sunlight needed varies.
Older individuals and dark-skinned people tend to produce less vitamin D in the skin (34, 35).
Also, geographic location and season are relatively crucial because vitamin D production is affected in places further away from the equator (35, 36)
However, it doesn’t take a lot of sun exposure to make vitamin D, and it’s best to limit your time in the sun to 10 to 15 minutes, exposing arms, legs, abdomen, and back.
The Skin Cancer Organization recommends that you only do this two to three times weekly, followed by sunscreen use. After that period, your body will get rid of any excess vitamin D, and you’d be introducing sun damage without any added benefit (37).
Keep in mind that the same process that helps your body synthesize vitamin D can cause DNA damage, sunburn, genetic mutations. This can cause wrinkles to develop and increase your risk for skin cancer (37).
But you can opt to consume supplements or foods that contain vitamin D.
Sunshine can help you meet the vitamin D requirements, but it’s important to limit sun exposure. During the winter, and for those living far from the equator, supplements may be needed.
While incidences of vitamin D toxicity are rare, getting too much can be harmful. It could lead to:
nauseavomitingmuscle weaknessconfusion loss of appetitedehydration kidney stones
Extremely high levels can cause:
kidney failureirregular heartbeatdeath
This is typically only seen in individuals who have accidentally or intentionally taken extremely high vitamin D doses for long periods (22, 38, 39).
The upper limit per the NIH is 4,000 IU daily for those ages 9 years and older.
A study of 17,000 people taking varying doses of vitamin D, up to 20,000 IU/day, to analyze the relationship between body weight and vitamin D needs, did not demonstrate any signs of toxicity.
Their blood levels were still lower than the upper range of normal, which is 100 ng/ml, or 250 nmol/l (27).
Speak with your healthcare provider before consuming more than the recommended daily allowance.