How much vitamin D do we need and how can we get it?

Photo of two people relaxing outdoors

Healthy people who spend enough time outdoors don’t need to worry about not getting enough vitamin D. Those who have a higher risk of developing a vitamin D deficiency can take supplements.

Vitamin D is important for healthy bones. It helps bones to absorb minerals that make them strong. Our bodies can usually produce the vitamin D they need themselves. All it takes is a few minutes of sunlight on our skin. We also get a small amount of vitamin D through our food.

So you don’t need to have your vitamin D levels checked regularly. There’s no health benefit unless there’s a specific reason to get them checked.

How much vitamin D do we need?

According to estimates by the German Nutrition Society (DGE), children and adults need 20 micrograms (20µg) of vitamin D per day to keep their bones healthy. Babies need roughly 10µg per day during their first year.

Sometimes the recommended daily amounts are expressed in International Units (IU):

  • 10µg is the same as 400 IU.
  • 20µg is the same as 800 IU.

You can convert doses between micrograms and International Units using a factor of 40 (see examples above). There are also free conversion calculators on the internet.

What can vitamin D levels tell us?

The level of vitamin D in your blood can be used to assess whether you have enough to keep your bones healthy. But there isn’t enough research to say what it can tell us about the risk of other illnesses.

The blood test measures how much 25-hydroxy vitamin D (25(OH)D) there is in your blood. The result is given in nanograms per milliliter (ng/ml), nanomoles per liter (nmol/l) or micrograms per liter (µg/l). You can convert the dose from one of these units to another using free conversion calculators on the internet.

The Robert Koch Institute (RKI) in Germany divides vitamin D levels into the following categories:

  • Sufficient: A level of at least 20ng/ml indicates that you have enough vitamin D to keep your bones healthy. Levels above 30ng/ml don’t provide any additional health benefits.
  • Sub-optimal: A level between 12ng/ml and below 20ng/ml can have a negative impact on bone health.
  • Insufficient: People with levels below 12ng/ml have a higher risk of developing rickets or osteomalacia. If they also have symptoms like bone pain, joint pain or muscle ache, they have a vitamin D deficiency. In elderly people, a vitamin D deficiency can make osteoporosis more likely. Osteomalacia and osteoporosis increase the risk of falling and breaking bones, especially in older people.

Some medical societies use a higher cut-off point – considering levels under 20ng/ml to be insufficient, for example.

Good to know:

You only have a vitamin D deficiency if your levels are low and you have symptoms like bone pain and muscle ache. Simply having low vitamin D levels doesn't mean you have a deficiency.

But it's important to be aware that the vitamin D levels measured in blood tests aren't always reliable. First, they can differ depending on how the lab measures them. And second, vitamin D levels change from season to season. So it's better to measure them several times throughout the year rather than just once. They drop naturally in the winter and then increase in the summer when our skin produces vitamin D again.

Does vitamin D protect us from other illnesses?

Vitamin D is important for healthy bones. That’s a known fact. But what about other illnesses?

A number of studies have concluded that when people who have sub-optimal vitamin D levels take supplements, it doesn’t protect them from illnesses like cardiovascular disease, diabetes, cancer or . And it doesn’t matter whether the vitamin D is taken with or without . But these studies were too short to judge the long-term effects of vitamin D because many of the illnesses they looked at take years to develop. Vitamin D did reduce the number of falls in some elderly people, though.

Another study looked at whether vitamin D can protect people from acute respiratory infections like colds or influenza (the flu). It found some that taking vitamin D on a daily or weekly basis could help prevent these types of – especially in people with levels below 10ng/ml.

There hasn’t been enough suitable research on how vitamin D affects other conditions such as sleep problems, dementia or autoimmune diseases.

Who can benefit from taking vitamin D supplements?

People who are healthy and spend enough time outdoors make enough vitamin D through their skin with the help of the sun’s UVB rays. We also get a small amount of vitamin D in our food.

But there are some groups of people who have trouble getting enough vitamin D. It can make sense for them to take vitamin D as a precaution:

It is estimated that people with dark skin need 10 to 15 times more exposure to UVB rays than light-skinned people do in order to produce enough vitamin D.

Some people aren't able to make vitamin D properly due to a chronic illness of the bowel, kidneys or liver – or because of certain medications they take. If this applies to you, it might be useful to take a supplement. Talk to your doctor about it first. Sometimes it’s enough to only take vitamin D in the fall or winter.

How can you improve your vitamin D levels?

You can do this in three ways:

  • Spend more time outdoors
  • Eat more foods that contain vitamin D
  • Take vitamin D supplements

Spending more time outdoors

Your body can make large amounts of vitamin D itself. All you need is sunlight and a small area of exposed skin. You can make enough vitamin D by, for example, exposing your face, hands and arms to sunlight about two to three times per week without sunscreen. If you know how long you can usually stay in the sun without getting a sunburn, spending half that amount of time in the sun should be enough. If you make more vitamin D than you need, your body can store it. This extra vitamin D is not harmful.

So you need sunlight to make vitamin D, but sunlight also increases your risk of skin cancer. Because of this, it's important to find a compromise and make sure your skin doesn’t turn red or burn when you're out in the sun. In the summer, the sun is particularly strong between 11am and 3pm.

Our bodies can’t make vitamin D indoors because the UVB rays we need from the sun don't go through window panes.

People who live in Germany and other Northern European countries can’t make vitamin D in the winter either because the sun is too low in the sky. But they usually store enough between March and October to be able to help them through the winter months.

Eating more foods that contain vitamin D

We can get a little vitamin D from our food too, but it’s not enough. That’s because there are only a few foods that contain large enough amounts of vitamin D. They include

  • fatty fish like herring, mackerel, salmon and trout,
  • innards like liver,
  • edible mushrooms like button mushrooms, porcini mushrooms and chanterelles, and
  • egg yolk.

Some foods (like margarine and other spreadable fats) are fortified with small amounts of vitamin D in Germany and other countries. In addition, mushrooms, baker’s yeast, “Hefebrot” bread and milk are allowed to be treated with ultraviolet light in Germany to increase their vitamin D content. Foods that have been fortified with vitamin D or treated with ultraviolet light have to be labeled accordingly.

Taking vitamin D supplements

Supplements are another way to get enough vitamin D. They come as tablets, capsules, sprays and drops. You can buy them without a prescription at drug stores, pharmacies, or from online shops. Some of them contain other vitamins or minerals too.

It is best to take the 20µg (800 IU) dose of vitamin D per day recommended by the DGE – even if some manufacturers recommend a different daily dose. Because our bodies need fat or oil to be able to absorb vitamin D, it’s best to take the supplements with a meal if they haven’t got any fat in them.

People who take too much vitamin D are likely to have side effects. Overdosing causes hypercalcemia, where there’s too much in the blood. Possible symptoms include nausea and vomiting, stomach cramps and loss of appetite. Extreme overdoses can lead to kidney stones and kidney damage, heart rhythm disorders (arrhythmias) or unconsciousness.

To prevent these side effects, it’s important that teenagers and adults don’t take more than 100µg of vitamin D (4000 IU) per day.

Bundesamt für Strahlenschutz (BfS). Konsentierte Empfehlung zu UV-Strahlung und Vitamin D. 2022.

Committee to Review Dietary Reference Intakes for Vitamin D and Calcium, Food and Nutrition Board. Dietary Reference Intakes for Calcium and Vitamin D. Washington (DC): National Academies Press (US); 2011.

Deutsche Gesellschaft für Ernährung (DGE), Österreichische Gesellschaft für Ernährung (ÖGE), Schweizerische Gesellschaft für Ernährung (SGE). D-A-CH: Referenzwerte für die Nährstoffzufuhr. Bonn: DGE; 2021.

Institute for Quality and Efficiency in Health Care (IQWiG, Germany). Blutwerte. Profitieren ältere Personen von einer regelmäßigen Bestimmung der Vitamin-B12- und Vitamin-D-Werte im Blut? (HTA kompakt: Das Wichtigste verständlich erklärt; HT20-04). 2022.

Institute for Quality and Efficiency in Health Care (IQWiG, Germany). HTA-Bericht: Blutwerte. Profitieren ältere Personen von einer regelmäßigen Bestimmung der Vitamin-B12- und Vitamin-D-Werte im Blut? (Health Technology Assessment on behalf of the IQWiG: HT20-04). 2022.

Kahwati LC, LeBlanc E, Weber RP et al. Screening for Vitamin D Deficiency in Adults: An Evidence Review for the U.S. Preventive Services Task Force. (AHRQ Evidence Syntheses; No. 201). 2021.

Martineau AR, Jolliffe DA, Greenberg L et al. Vitamin D supplementation to prevent acute respiratory infections: individual participant data meta-analysis. Health Technol Assess 2019; 23(2): 1-44.

Robert Koch-Institut (RKI). Antworten des Robert Koch-Instituts auf häufig gestellte Fragen zu Vitamin D. 2019.

IQWiG health information is written with the aim of helping people understand the advantages and disadvantages of the main treatment options and health care services.

Because IQWiG is a German institute, some of the information provided here is specific to the German health care system. The suitability of any of the described options in an individual case can be determined by talking to a doctor. informedhealth.org can provide support for talks with doctors and other medical professionals, but cannot replace them. We do not offer individual consultations.

Our information is based on the results of good-quality studies. It is written by a team of health care professionals, scientists and editors, and reviewed by external experts. You can find a detailed description of how our health information is produced and updated in our methods.

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Created on November 11, 2024

Next planned update: 2027

Publisher:

Institute for Quality and Efficiency in Health Care (IQWiG, Germany)

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