In the UK, the NHS advises that everyone should consider taking a daily supplement of 10 micrograms of vitamin D during autumn and winter, roughly October to March. From late March to the end of September most people can make enough vitamin D from sunlight on their skin, but some groups are advised to take a supplement all year round.
The two numbers to understand are the dose and the upper limit. A dose of 10 micrograms is the same as 400 IU (international units). The NHS says adults should not take more than 100 micrograms (4,000 IU) a day, and the limits are lower for children. Many supplements sold online contain far more than 10 micrograms per serving, so check the label rather than assuming that more is better.
This guide is general information, not medical advice. If you have a health condition, take other medicines or are unsure what dose suits you, ask a pharmacist or your GP.
Who is advised to take vitamin D
NHS guidance groups people like this:
- Everyone over 4: consider 10 micrograms a day in autumn and winter.
- People who are rarely outdoors, for example if they are frail, housebound or live in a care home: consider 10 micrograms a day all year.
- People who usually cover most of their skin when outdoors: consider a supplement all year.
- People with dark skin, for example of African, African-Caribbean or South Asian origin: may not make enough vitamin D from sunlight and should consider a supplement all year.
- Children aged 1 to 4: 10 micrograms a day all year.
- Babies under 1: 8.5 to 10 micrograms a day, unless they drink more than 500 ml of infant formula a day, because formula already contains vitamin D.
Some people cannot take vitamin D safely in standard amounts, for example because of certain kidney conditions, so check with a doctor if that applies to you.
Micrograms and IU: reading the label
Labels use micrograms (written as mcg or µg), IU, or both. The conversion is simple: 1 microgram equals 40 IU.
| Label says | In micrograms | How it compares with NHS advice |
|---|---|---|
| 400 IU | 10 mcg | The daily amount the NHS suggests for most people |
| 1,000 IU | 25 mcg | Above 10 mcg, below the adult upper limit |
| 2,500 IU | 62.5 mcg | Well above the advised amount; check with a pharmacist |
| 4,000 IU | 100 mcg | The maximum the NHS says adults should take a day |
| 5,000 IU | 125 mcg | Above the adult upper limit for daily use |
Check whether the dose is per capsule, per drop, per spray or per serving of several units. A product that says 1,000 IU “per serving” might need two capsules to reach that amount. If you also take a multivitamin from the multivitamins range or a fish oil with added vitamin D, add those amounts together. The same applies to combined products in the minerals section that pair vitamin D with calcium or magnesium.
D3 or D2
Most supplements contain vitamin D3 (cholecalciferol). Traditional D3 comes from lanolin, the oil in sheep’s wool, so it is not vegan. Vegan D3 made from lichen is widely available, and vitamin D2 (ergocalciferol) is also plant based. If you avoid animal products, look for “vegan” on the label and check the capsule shell, since softgels are often made with gelatine.
Capsules, softgels, drops or sprays
The form makes little difference to the vitamin itself; it is mainly about what you find easy to take every day.
- Capsules and tablets: easy to dose and usually the cheapest per day. Check the shell material if you are vegetarian or vegan.
- Softgels: vitamin D dissolved in oil inside a soft capsule, often small and easy to swallow.
- Drops and liquids: useful for children and people who dislike swallowing pills. Measure carefully, since one drop or one dropper can mean very different amounts.
- Oral sprays: sprayed into the mouth; convenient, but check the dose per spray and how many sprays the bottle holds.
The vitamin D range includes all of these, and the general tablets section lists further vitamin and mineral tablets. For more on forms, the blog has a separate article on capsules, tablets, drops and gummies.
Children and babies
Choose a product made for the age group, with a clear dose per drop or per spray, and stay within the limits for children. The NHS says children aged 1 to 10 should not have more than 50 micrograms a day, and babies under 12 months no more than 25 micrograms a day. Families who qualify for the Healthy Start scheme can get free vitamin supplements for children, so check whether you are eligible before buying.
Comparing price and value
Compare the cost per daily dose rather than the price per pot. Divide the price by the number of days the pack lasts at the dose you plan to take. A cheap pot of high strength capsules may last longer, but if the strength is far above 10 micrograms you may not want a capsule every day. Store vitamin D away from heat and light, and look at the best before date if you are buying a large pack. The guide to vitamin C serums covers a different use of vitamins, in skincare.
Quick checklist
- 10 micrograms (400 IU) a day in autumn and winter for most people.
- All year for people who are rarely outdoors, cover their skin or have dark skin.
- No more than 100 micrograms (4,000 IU) a day for adults.
- Check the dose per capsule, drop or spray, and add up other supplements.
- Vegan D3 or D2 if you avoid animal products.
- Child-specific products and lower limits for children.
- Ask a pharmacist or GP if you have a health condition or take medicines.
Common questions
Can I get enough vitamin D from food?
It is hard. Oily fish, red meat, egg yolks and fortified foods contain some, but the NHS notes that it is difficult to get enough from food alone, which is why it recommends a supplement in autumn and winter.
Is a higher strength supplement better?
Not necessarily. Taking too much vitamin D over a long period can cause too much calcium to build up in the body. Stay within the NHS limits unless a doctor has advised a different dose.
Should I take vitamin D in summer?
Most people make enough from sunlight between late March and the end of September. People in the year round groups above should keep taking it.
