Vitamin D in Winter: How Much to Take in the UK (NHS Advice Explained)

What vitamin do you get from the sun?

The vitamin you get from the sun is vitamin D. Your skin makes it when UVB rays from sunlight reach it outdoors. The NHS says most people in the UK can make enough from late March or early April to the end of September, but from October to early March the sun isn’t strong enough, so a supplement is advised.

Glass blocks UVB, so sun through a window doesn’t count (more below). Vitamin D contributes to the normal function of the immune system and to the maintenance of normal bones.

Why vitamin D matters in winter

Your body makes most of its vitamin D from sunlight on your skin. The NHS says that from about late March or early April to the end of September, most people can make all the vitamin D they need this way. But between October and early March, we do not make enough from sunlight in the UK, and only a small number of foods contain it.

Vitamin D contributes to the maintenance of normal bones, teeth and muscle function, and to the normal function of the immune system. That is why the government advises a daily supplement through the darker months.

Can you get vitamin D through a window?

No, not through ordinary window glass. Your skin makes vitamin D from the sun’s UVB rays, and window glass absorbs UVB, so sunlight through a window does not make vitamin D in your skin. Sitting by a sunny window, in a conservatory or in the car does not count. From late March to September you need sun directly on your skin outdoors. From October to early March the UK sun is too weak even outside, which is why the NHS advises a supplement, and all year if you are rarely outdoors.

Why are experts urging people to take vitamin D this winter?

Because from October to early March the UK sun is too weak for your skin to make enough vitamin D, so the NHS advises everyone to consider a daily 10 microgram (400 IU) supplement. In late October 2026 the Royal Osteoporosis Society repeated the call: everyone should consider a daily supplement from the end of September to the beginning of April.

Low levels are common, especially in teenage girls: in the latest UK national survey (2019 to 2023), 26% of girls aged 11 to 18 were deficient, and experts such as Professor Martin Hewison of the University of Birmingham have called for routine winter supplements for some groups. See vitamin D deficiency in young women.

Some people need it all year: the NHS lists anyone rarely outdoors, anyone who covers most of their skin outside and people with dark skin (see below), and the Royal Osteoporosis Society adds that it may help in pregnancy and breastfeeding. Don’t take more than 100 micrograms (4,000 IU) a day.

A plain vitamin D3 supplement is the simple choice for most people. If you’d also like CBD, Evopure’s Evolabs Mint CBD Oil + Vit D3 gives 10µg (400 IU) of vegan D3 per half pipette (200% NRV), sold in the 1,000mg strength.

How much vitamin D should I take in the UK?

For most adults, 10 micrograms a day from October to March is enough. Higher doses are only for people a doctor has advised, for example after a blood test shows a deficiency.

Who should take vitamin D all year?

The NHS advises a daily 10 microgram supplement throughout the year if you:

• are not often outdoors, for example if you are frail, housebound or live in a care home
• usually wear clothes that cover most of your skin when outside
• have dark skin, for example if you have an African, African-Caribbean or south Asian background

All children aged 1 to 4, and babies (unless they have more than 500ml of formula a day), should also have a daily supplement all year.

Micrograms vs IU explained

Labels show vitamin D in either micrograms (mcg or µg) or International Units (IU). The conversion is simple: 1 microgram = 40 IU.

• 10 micrograms = 400 IU (the NHS daily amount)
• 25 micrograms = 1,000 IU
• 100 micrograms = 4,000 IU (the upper limit for adults)

A microgram is a thousand times smaller than a milligram, so don’t confuse mcg with mg.

Vitamin D3 vs D2: which is better?

There are two main forms in supplements:

• Vitamin D3 (cholecalciferol): the form your skin makes. Usually from lanolin (sheep’s wool), but vegan D3 from lichen or algae is also available.
• Vitamin D2 (ergocalciferol): from plants and fungi, and always vegan.

A 2012 review led by researchers at the University of Surrey found that D3 generally raised vitamin D levels in the blood more effectively than D2, especially when given in larger, less frequent doses. With daily doses the difference was smaller. For most people, a daily D3 supplement is a sensible choice.

Food sources of vitamin D

Only a few foods contain vitamin D, which is why diet alone rarely covers winter needs. The NHS lists:

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

Pregnant women should avoid liver and liver products because of their high vitamin A content.

For micrograms per portion of each food and the vegan options, see our full guide to vitamin D foods.

Signs you may be low in vitamin D

Many people with low vitamin D have no obvious symptoms. Over time, a lack of vitamin D can lead to bone pain and muscle weakness, and in children it can cause rickets. Symptoms such as tiredness, low mood, hair loss or weight gain are searched for a lot, but they have many causes and are not reliable signs on their own.

iIf you are worried, speak to your GP, who can arrange a blood test if needed. Don’t start high-dose vitamin D without medical advice.

Feeling flat as the nights draw in is common. See our guide to the winter blues for practical ways to feel better.

Can you take too much vitamin D?

Yes, from supplements. The NHS warns that taking too much over a long period can cause too much calcium to build up in the body (hypercalcaemia), which can weaken bones and damage the kidneys and heart. You cannot get too much vitamin D from sunlight.

Add up every product that contains vitamin D, including multivitamins and fortified drinks, and stay at 100 micrograms (4,000 IU) a day or less unless a doctor advises otherwise. Some medical conditions mean you may not be able to take as much, so check with your GP if that applies to you.

Is 10,000 IU too much, and what are the warning signs? See our full guide to taking too much vitamin D.

How to take vitamin D

• Take it with a meal. Vitamin D is fat-soluble, so it is absorbed better with food that contains some fat.
• Any time of day works. Pick a time you will remember, such as breakfast.
• Start in October and carry on until March.
• Choose a format you will actually take: tablets, sprays, drops or an oil you already use. We compare six UK options in the best vitamin D supplement in the UK.
• Pairing with magnesium is fine. Many people take both in winter. See magnesium and vitamin D together.

Our Mint CBD Oil with Vitamin D3 provides 10 micrograms (400 IU) of algae-based, vegan vitamin D3 per half pipette (200% of the nutrient reference value) alongside high-quality, tested CBD. That is the NHS 10 microgram daily figure, well under the 100 microgram upper limit. If you take another vitamin D product too, count both towards your daily total. Read why we added vitamin D3 to our mint oil.

Related guides

• Caught a cold anyway? See how to sleep with a cold.
• Blue Monday 2027 and the January blues.
• Vitamin D deficiency symptoms, tests and treatment.
• Building better habits this winter? Our Winter Arc plan puts vitamin D alongside sleep, training and daylight.
• The best time to take vitamin D, including morning vs night and taking it with food.
• Note that a SAD lamp won’t give you vitamin D, because light boxes are UV-free.
• For where vitamin D fits alongside omega-3, B12 and the rest, see supplements for men over 40 and 50.
• Do you need a multivitamin as well as vitamin D?
• Calcium and vitamin D: do you need a calcium supplement?
• If you like to have your winter supplements in before the dark months, read whether Black Friday is a good time to stock up.
• Flu jab side effects (UK).
• For a side-by-side table of the two forms, vegan options and whether to add K2, see vitamin D vs D3.
• Vitamin D isn’t a cold remedy; for what actually helps, see our guide to the difference between a cold and flu.
• Wondering whether low vitamin D is behind dry, itchy winter skin? Our dry skin guide looks at which deficiencies really affect the skin.
• The best vitamins for the immune system, with NHS amounts.
• Vitamin D is only one possible factor. For the full list of reasons people feel worn out in later life, see tired all the time at 50, 60 or 70?
• Women can see where vitamin D fits with iron, B12 and calcium in our guide to supplements for women over 50.
• Wondering about adding K2? Read what vitamin K2 is and whether to take D3 with K2.