Is it better to take vitamin d every day or once a week

April 25, 2017
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DEAR MAYO CLINIC: I have heard different recommendations from different sources regarding vitamin D. One doctor told my husband that everyone living in the Northern Hemisphere should take a vitamin D supplement every day, even in the summer. What do you recommend?

ANSWER: Understanding how much vitamin D you need can be confusing because there are different recommendations about how much vitamin D adults should get. Using the recommendations that fall on the low end, many adults don’t get the amount of vitamin D they should. Because few foods contain vitamin D naturally, eating foods fortified with vitamin D and taking a supplement may be beneficial.

Vitamin D is important because it helps your body sustain normal levels of calcium and phosphorus. Because it works as a key that allows your body to absorb calcium, vitamin D plays a critical role in forming and maintaining healthy bones. It also helps keep your muscles, nerves and immune system healthy.

Research suggests that consistently getting enough vitamin D can significantly lower the risk for the bone-thinning disease osteoporosis. Low vitamin D also is associated with falls, multiple sclerosis, rheumatoid arthritis, chronic pain, diabetes, high blood pressure, cardiovascular disease and some cancers. However, an association does not mean low vitamin D causes these conditions, or that taking a vitamin D supplement will adequately prevent or treat them.

Vitamin D is found in some foods, such as egg yolks, cheese, cod liver oil, beef liver and fatty fish like tuna, salmon, sardines, herring and mackerel. But the amount of vitamin D in these foods is quite small. In the U.S., many people get the bulk of their dietary vitamin D from foods that are fortified with it, including milk, cereals and some brands of yogurt and orange juice.

In general, even with fortified foods, diet usually doesn’t provide enough vitamin D. And certain health conditions that affect the gastrointestinal tract may decrease the absorption of vitamin D and predispose to low vitamin D blood levels. You also can get vitamin D through direct exposure to sunlight, although the amount of sun you need to get enough vitamin D can vary greatly.

For people in northern climates or those who spend most of their time indoors, adequate exposure to sunlight can be hard to get. Also, if you regularly wear sunscreen with a sun protection factor higher than eight — a wise move to protect your skin from cancer — or if you have a darker skin tone, you may not be absorbing vitamin D, even when you are out in the sunshine.

Recommendations for how much daily vitamin D adults need through diet have changed over the years. Currently, different recommendations exist. The Institute of Medicine has placed the recommended dietary allowance, or RDA, for vitamin D at 600 international units (IU) per day for young adults and 800 IU per day for adults older than 70. Other experts suggest that adults’ vitamin D needs are much higher. For example, the Endocrine Society recommends up to 1,500 to 2,000 IU of vitamin D daily for adults.

Mayo Clinic recommends that adults get at least the RDA of 600 IU. However, 1,000 to 2,000 IU per day of vitamin D from a supplement is generally safe, should help people achieve an adequate blood level of vitamin D, and may have additional health benefits. While there are no guidelines for checking your vitamin D blood level, it may be prudent in people with osteoporosis or certain other health conditions. Discuss with your health care provider if it may be beneficial to check your vitamin D level.

If you have ongoing health concerns or a chronic health condition, talk to your health care provider before you begin taking any dietary supplement, including vitamin D. He or she can help you decide if supplements are appropriate for your situation. — Dr. Donald Hensrud, Preventive Medicine, Mayo Clinic, Rochester, Minnesota

Vitamin D helps regulate the amount of calcium and phosphate in the body.

These nutrients are needed to keep bones, teeth and muscles healthy.

A lack of vitamin D can lead to bone deformities such as rickets in children, and bone pain caused by a condition called osteomalacia in adults.

Government advice is that everyone should consider taking a daily vitamin D supplement during the autumn and winter.

People at high risk of not getting enough vitamin D, all children aged 1 to 4, and all babies (unless they're having more than 500ml of infant formula a day) should take a daily supplement throughout the year.

Information:

There have been some reports about vitamin D reducing the risk of coronavirus (COVID-19). But there is currently not enough evidence to support taking vitamin D solely to prevent or treat COVID-19.

Good sources of vitamin D

From about late March/early April to the end of September, most people should be able to make all the vitamin D they need from sunlight.

The body creates vitamin D from direct sunlight on the skin when outdoors.

But between October and early March we do not make enough vitamin D from sunlight. Read more about vitamin D and sunlight.

Vitamin D is also found in a small number of foods.

Sources include:

oily fish – such as salmon, sardines, herring and mackerel
red meat
liver
egg yolks
fortified foods – such as some fat spreads and breakfast cereals

Another source of vitamin D is dietary supplements.

In the UK, cows' milk is generally not a good source of vitamin D because it is not fortified, as it is in some other countries.

How much vitamin D do I need?

From about late March/early April to the end of September, the majority of people should be able to make all the vitamin D they need from sunlight on their skin.

Children from the age of 1 year and adults need 10 micrograms of vitamin D a day. This includes pregnant and breastfeeding women, and people at risk of vitamin D deficiency.

Babies up to the age of 1 year need 8.5 to 10 micrograms of vitamin D a day.

A microgram is 1,000 times smaller than a milligram (mg). The word microgram is sometimes written with the Greek symbol μ followed by the letter g (μg).

Sometimes the amount of vitamin D is expressed as International Units (IU). 1 microgram of vitamin D is equal to 40 IU. So 10 micrograms of vitamin D is equal to 400 IU.

Should I take a vitamin D supplement?

Advice for adults and children over 4 years old

During the autumn and winter, you need to get vitamin D from your diet because the sun is not strong enough for the body to make vitamin D.

But since it's difficult for people to get enough vitamin D from food alone, everyone (including pregnant and breastfeeding women) should consider taking a daily supplement containing 10 micrograms of vitamin D during the autumn and winter.

Between late March/early April to the end of September, most people can make all the vitamin D they need through sunlight on their skin and from a balanced diet.

You may choose not to take a vitamin D supplement during these months.

People at risk of vitamin D deficiency

Some people will not make enough vitamin D from sunlight because they have very little or no sunshine exposure.

The Department of Health and Social Care recommends that adults and children over 4 take a daily supplement containing 10 micrograms of vitamin D throughout the year if they:

are not often outdoors – for example, if they're frail or housebound
are in an institution like a care home
usually wear clothes that cover up most of their skin when outdoors

If you have dark skin – for example you have an African, African-Caribbean or south Asian background – you may also not make enough vitamin D from sunlight.

You should consider taking a daily supplement containing 10 micrograms of vitamin D throughout the year.

Advice for infants and young children

The Department of Health and Social Care recommends that babies from birth to 1 year of age should have a daily supplement containing 8.5 to 10 micrograms of vitamin D throughout the year if they are:

breastfed
formula-fed and are having less than 500ml (about a pint) of infant formula a day, as infant formula is already fortified with vitamin D

Children aged 1 to 4 years old should be given a daily supplement containing 10 micrograms of vitamin D throughout the year.

You can buy vitamin D supplements or vitamin drops containing vitamin D (for under 5s) at most pharmacies and supermarkets.

Women and children who qualify for the Healthy Start scheme can get free supplements containing vitamin D.

See the Healthy Start website for more information.

What happens if I take too much vitamin D?

Taking too many vitamin D supplements over a long period of time can cause too much calcium to build up in the body (hypercalcaemia). This can weaken the bones and damage the kidneys and the heart.

If you choose to take vitamin D supplements, 10 micrograms a day will be enough for most people.

Do not take more than 100 micrograms (4,000 IU) of vitamin D a day as it could be harmful. This applies to adults, including pregnant and breastfeeding women and the elderly, and children aged 11 to 17 years.

Children aged 1 to 10 years should not have more than 50 micrograms (2,000 IU) a day. Infants under 12 months should not have more than 25 micrograms (1,000 IU) a day.

Some people have medical conditions that mean they may not be able to safely take as much. If in doubt, you should consult your doctor.

If your doctor has recommended you take a different amount of vitamin D, you should follow their advice.

You cannot overdose on vitamin D through exposure to sunlight. But always remember to cover up or protect your skin if you're out in the sun for long periods to reduce the risk of skin damage and skin cancer.

Page last reviewed: 03 August 2020
Next review due: 03 August 2023

Is vitamin D better daily or weekly?

Conclusions: Supplementation with vitamin D can be achieved equally well with daily, weekly, or monthly dosing frequencies. Therefore, the choice of dose frequency can be based on whichever approach will optimize an individual's adherence with long-term vitamin D supplementation.

What happens when you take vitamin D everyday?

However, taking too much vitamin D in the form of supplements can be harmful. Children age 9 years and older, adults, and pregnant and breastfeeding women who take more than 4,000 IU a day of vitamin D might experience: Nausea and vomiting. Poor appetite and weight loss.

Should I take a vitamin D pill every day?

Why vitamin D should be taken once a week?

It helps maintain healthy and strong bones and teeth. This is a high dose of vitamin D to be taken once weekly and not meant for daily consumption. It should be taken for a limited period only under a doctor's guidance. It is used for the treatment and prevention of vitamin D deficiency.