Vitamin D Supplements

How much vitamin D should you take a day?

The NHS says adults and children from the age of 1 need 10 micrograms (400 IU) of vitamin D a day, and adults should not take more than 100 micrograms (4,000 IU) a day, as that could be harmful. Children aged 1 to 10 should not have more than 50 micrograms (2,000 IU) a day, and babies under 12 months no more than 25 micrograms (1,000 IU).

Babies up to 1 year need 8.5 to 10 micrograms a day, but the NHS says formula-fed babies do not need a supplement if they have more than 500ml of infant formula a day. Browse kids' vitamins.

What do 1,000 IU and 4,000 IU mean on a label?

IU (international units) and micrograms are two ways of writing the same amount: the NHS says 1 microgram of vitamin D is equal to 40 IU. So a 1,000 IU tablet contains 25 micrograms, two and a half times the NHS daily amount, and a 4,000 IU tablet contains 100 micrograms, the adult upper limit.

Labels may also show %NRV (Nutrient Reference Value). The NRV for vitamin D is 5 micrograms, so the NHS daily amount of 10 micrograms already shows as 200%.

"Some supplements advertise 1,000% or more of the Nutrient Reference Value, making them appear more powerful," says Andy Arshad, who runs SupplementHQ. "But a higher dose doesn't automatically mean better results, and in some cases, excessive intake can be harmful." Our guide to reading a supplement label explains %NRV in more detail.

Is vitamin D the same as vitamin D3?

Vitamin D3 (cholecalciferol) is one form of vitamin D, and vitamin D2 (ergocalciferol) is another. The British Dietetic Association says vitamin D3 is the most effective, while D2 is a plant-based alternative suitable for vegetarians and vegans.

"Vitamin D2 and D3 aren't identical, and customers may not realise the difference," says Andy. Most of the products in this collection use D3; check the label for which form you're buying.

Is there a vegan vitamin D?

Yes: the Vegan Society says vitamin D2 is not derived from animals, and vegan vitamin D3 can be derived from lichen. Many D3 supplements, though, use D3 made from lanolin, which comes from sheep's wool.

So "D3" on its own doesn't tell you whether a product is vegan. Look for a vegan label or a lichen source, such as the plant-based D3 liquid and vegan D3 + K2 products in this collection.

Should you take vitamin D with K2?

That's your choice, but there is no NHS recommendation to take vitamin K2 alongside vitamin D. The NHS says you should be able to get all the vitamin K you need from a varied and balanced diet, and that 1mg or less a day of vitamin K from supplements is unlikely to cause any harm.

D3 + K2 products are popular, and we stock plenty of them, but we don't claim the combination does more than vitamin D alone. If you take blood-thinning medication, speak to your GP or pharmacist before taking any supplement that contains vitamin K.

Tablets, spray, drops or gummies?

Choose the format you'll actually take every day, then compare the amount of vitamin D per daily dose and the cost per day. Sprays, drops and gummies are convenient, but gummies in particular often cost more per day and can contain added sugars.

"We think customers should compare the actual amount of active ingredients they're getting, rather than just the format or marketing," says Andy.

How to compare value (example figures, not real products): a £6 pot of 90 vitamin D tablets, one a day, costs about 7p a day. A £12 pot of 60 gummies, two a day for the same amount, costs 40p a day, nearly six times as much for the same dose. Browse vitamin gummies.

When should you take vitamin D?

The NHS says everyone should consider a daily vitamin D supplement in autumn and winter, because between October and early March we do not make enough vitamin D from sunlight. People who are rarely outdoors or have darker skin should consider one all year round, and all children aged 1 to 4 should have one every day.

From about late March or early April to the end of September, the NHS says most people can make the vitamin D they need from sunlight. Follow the directions on the label for how and when in the day to take your product.

Can you take too much vitamin D?

Yes. The NHS says taking too many vitamin D supplements over a long time can cause too much calcium to build up in the body, which can weaken the bones and damage the kidneys and the heart.

The easiest way to go over is to take more than one product: the British Dietetic Association advises not taking other supplements that also contain vitamin D, such as cod liver oil or a multivitamin, alongside a vitamin D supplement. Add up the amount across everything you take, and speak to your GP or pharmacist first if you have a medical condition or take medication.

Which is the best vitamin D supplement?

The best one for you contains the amount you need, in a form that suits your diet, at a sensible cost per day. A higher dose, a premium brand or a more expensive format doesn't automatically make a product better.

"Sometimes the premium is justified by formulation, testing or ingredient quality, but sometimes customers are paying mainly for branding," says Andy. Start with the amount per daily dose, then check the form (D3 or D2, vegan or not), whether you want K2 added, and the cost per day. If you're unsure what you need, our guide to what supplements you actually need is a good place to start.

We sell the products on this page. That's our commercial interest, and it's why we show the NHS advice alongside them. This page is general information for adults, not personalised medical advice. Food supplements should not replace a varied, balanced diet.

Written by Andy Arshad, SupplementHQ. Last reviewed 11 October 2026.