How much sun do you need for vitamin D?

There is no single number, because it depends on where you live, the season, the time of day and your skin. One range, which the US National Institutes of Health reports some experts suggest, is about 5 to 30 minutes of sun on the face, arms, hands and legs without sunscreen, between 10 a.m. and 4 p.m., daily or at least twice a week. In winter at higher latitudes the sun makes too little vitamin D or none, which is why the UK's NHS advises everyone there to consider a daily 10 microgram supplement in autumn and winter.

The same NIH summary calls UV radiation a carcinogen and the most preventable cause of skin cancer. So the aim is short, regular exposure, and never a sunburn. I have kept this page to what official bodies and the largest trials say, because vitamin D is an easy subject to oversell.

How your skin makes vitamin D#

Ultraviolet B light, at wavelengths of roughly 290 to 320 nanometers, reaches uncovered skin and turns a compound there, 7-dehydrocholesterol, into previtamin D3, which becomes vitamin D3. The liver and then mainly the kidneys convert it into the active form. Its best-established job is helping the body absorb calcium and build bone.

UVB does not pass through glass. A sunny window makes no vitamin D.

Why season, latitude, skin tone, clothing and age matter#

The UVB that reaches you changes with the season, the time of day, the length of the day, cloud cover and smog, and your skin's melanin and any sunscreen change how much of it you use.

Latitude and season. In a 1988 experiment, skin samples left in cloudless sunshine in Boston, at 42 degrees north, made no previtamin D3 from November through February. In Edmonton, at 52 degrees north, the gap ran from October through March. Further south, at 34 and 18 degrees north, the sun still worked in midwinter. The NHS puts the UK's window at about late March or early April to the end of September.

Skin tone. More melanin reduces the skin's ability to make vitamin D from sunlight. The NHS advises people with dark skin, for example from an African, African-Caribbean or south Asian background, to consider a supplement all year. In pooled European data, darker-skinned groups were 3 to 71 times more likely than white populations to have very low levels.

Clothing and time indoors. People who are homebound, who wear long robes, dresses or head coverings for religious reasons, or whose work keeps them out of the sun are unlikely to get enough from sunlight alone.

Age. The skin's ability to make vitamin D declines with age, and older people tend to spend more time indoors.

How common is vitamin D deficiency?#

Definitions first. The US Food and Nutrition Board considers a blood level of 50 nmol/L (20 ng/mL) or more enough for most people, and says the risk of deficiency rises below 30 nmol/L (12 ng/mL). Where the line is drawn changes how common deficiency looks.

• Europe. Standardized data on 55,844 people found 13.0% below 30 nmol/L across the year, 17.7% among those tested from October to March and 8.3% in summer. Using the higher line of 50 nmol/L, it was 40.4%.
• India. Strong sun does not guarantee enough. Among 1,403 adults aged 30 and over in and around Delhi, the median level was 7.7 ng/mL in the city and 16.2 ng/mL in nearby rural areas, and 71% of city adults were severely deficient, below 10 ng/mL, against 20% of rural adults. India's national nutrition survey of 2016–18 found deficiency in 13.7% of preschool children, 18.2% of school-age children and 23.9% of adolescents. A 2026 systematic review argues that global cut-offs overstate the problem in India and that mass screening and supplementation of people without symptoms should be discouraged, so treat the larger figures with care.
• The US. Most people get less than the recommended amount from food, yet the NIH notes that most have sufficient blood levels by the Food and Nutrition Board's thresholds, partly because of sun.

Official advice, side by side#

Where	Advice for adults	From
UK	Consider 10 micrograms (400 IU) a day in autumn and winter; all year with dark skin, little time outdoors or skin usually covered	NHS
US	15 micrograms (600 IU) a day up to age 70; 20 micrograms (800 IU) over 70	NIH Office of Dietary Supplements
European Union	15 micrograms a day, set assuming little sun	EFSA
India	600 IU (15 micrograms) a day	ICMR-NIN, 2020
Australia	A few minutes outdoors on most days when the UV Index is 3 or above; when it is below 3, time outdoors in the middle of the day with some skin uncovered	Cancer Council Australia

The NIH notes that countries' guidelines differ because the biology is incompletely understood and the guidelines serve different purposes. Follow the advice where you live.

How much is too much?#

More is not better. The NIH, EFSA and the NHS all put the upper limit for adults at 100 micrograms (4,000 IU) a day. The NHS warns that taking too much for a long time can make calcium build up in the body. Treating a confirmed deficiency is a different matter, and it is a doctor's decision, made with a blood test.

Vitamin D supplements can interact with some medicines, including orlistat, statins, steroids and thiazide diuretics. Tell the doctor or pharmacist what else you take, and never stop a prescribed medicine on your own.

Sun without sunburn#

The NHS says you cannot overdose on vitamin D from sunlight. Sunburn and skin cancer are the risks of too much sun, and none of the official advice asks for a tan.

• In the UK the sun is strongest between 11 a.m. and 3 p.m. from March to October. The NHS advice is shade at those hours, sunscreen of at least SPF 30, and never to burn.
• Cancer Council Australia advises sun protection whenever the UV Index is 3 or above, and says overexposure to UV is never recommended, even if you have a vitamin D deficiency.
• Sunscreen and vitamin D can coexist. Cancer Council Australia says studies show sunscreen has minimal impact on vitamin D levels over time.

Short and regular beats long and rare.

Does vitamin D help mood or energy?#

Lower vitamin D levels are linked with depression in observational studies, but the NIH's reading of the trials is plain: supplements have not been shown to prevent depression or treat depressive symptoms. The largest trial, VITAL-DEP, gave 18,353 adults aged 50 or over either 2,000 IU of vitamin D3 a day or a placebo, for a median of 5.3 years. There was no difference in depression or in mood scores.

Energy is less studied. In one trial of 120 otherwise healthy adults who were both tired and deficient, a single dose of vitamin D eased fatigue more than placebo after four weeks: 72% reported improvement, against 50% on placebo. It is one small, short trial, and it fits a plain rule: correcting a real deficiency can lift the tiredness it causes, while in the large trials of people not selected for deficiency, vitamin D did not lift mood.

The Endocrine Society's 2024 guideline suggests that healthy adults under 75 should not take more than the recommended intake to prevent disease.

Morning daylight is a separate benefit#

Vitamin D comes from UVB on skin. The body clock runs on light reaching the eyes, through a pathway from the retina that keeps it in step with the day. Outdoor light can reach 100,000 lux in direct sun and 25,000 lux in full daylight, while a standard office is around 500 lux. In summer a walk can do both jobs; in winter, when sunlight at higher latitudes makes little or no vitamin D, daylight still sets the clock. How to sleep better and time outside go further.

Get tested rather than guessing#

If you belong to one of the groups above, have symptoms, or have been tired for weeks, ask a doctor whether a blood test for vitamin D, called 25-hydroxyvitamin D, makes sense. The Endocrine Society suggests against routine testing for people with no particular reason, and the NIH notes that results vary between laboratory methods, so a doctor is the right person to order it and read it. A test turns a guess into a number. Tired all the time covers the other causes worth checking at the same visit.

Questions people ask#

Can you get vitamin D through a window?#

No. UVB does not pass through glass.

Does sunscreen stop you making vitamin D?#

Not in practice. The NIH says sunscreens of SPF 8 or more appear to block the UV that makes vitamin D, but people usually apply too little, miss patches and do not reapply, so skin probably still makes some. Cancer Council Australia says sunscreen has minimal impact on levels over time.

Can you get too much vitamin D from the sun?#

The NHS says no. Too much comes from supplements, which is why the upper limit for adults is 100 micrograms a day.

Will vitamin D lift low mood?#

Not in the large trials of people who were not selected for deficiency. If low mood has lasted for weeks, see a doctor.

Vitamin D will not end a habit. What it can do, if you were short of it, is remove one reason the evenings feel heavy, and a tired, heavy evening is exactly the kind of state that works as a cue. Stop first, and let the body come back alongside it: thirty days is the plan, and the body is the lesson on sleep, light and movement.