Best Vitamin D Supplement UK (2026): NHS Dose, D3 vs K2, and Tested Picks

Our picks at a glance

Grades describe the product. Vitamin D itself has strong evidence for preventing deficiency; "Promising" here means the ingredient is well supported but the product has no published independent test.

How much vitamin D do you need in the UK?

The NHS says adults and children over one need 10 micrograms (mcg) a day, which is 400 IU (international units; 1mcg = 40 IU). From late March to the end of September most people make enough from sunlight on their skin. From October to early March the sun in the UK is too weak, so the NHS advises everyone to consider a daily supplement.

Some people should consider taking it all year:

• people who are rarely outdoors, such as those who are housebound or in a care home
• people who usually cover most of their skin outdoors
• people with dark skin, such as those of African, African-Caribbean or South Asian background

The NHS also sets a ceiling: do not take more than 100mcg (4,000 IU) a day unless a doctor tells you to, because too much over a long time can raise calcium in the blood and damage the kidneys and heart. The 10mcg figure comes from the SACN vitamin D report, the UK's expert review.

How we chose

We checked UK brand sites in October 2026 and recorded the dose, form and price for each product. We ranked them on:

• Dose relative to NHS advice: 10mcg scores best for everyday use; 25mcg is acceptable; 100mcg products are flagged.
• Form: D3 (cholecalciferol), ideally with the source stated.
• Independent testing: we looked for Informed Sport or similar. Only one vitamin D product we found showed it.
• Price per month and no unnecessary extras.

Which vitamin D supplement should you buy?

Viridian Vitamin D3 400iu: best overall

The only product we found that delivers exactly the NHS's 10mcg per capsule, using vegan D3 from lichen with no fillers. The 90-capsule pot (£15.50) covers a full winter and then some. Caveat: there is no published independent test, so the grade reflects the ingredient and dose rather than certification.

Vitl Vitamin D3 1000iu: best budget

Vegan-friendly 25mcg softgels for £5.95 a month, with no preservatives or bulking agents. Caveat: 25mcg is more than most people need. It is comfortably below the upper limit, but you could take one every other day and still be above the NHS baseline on average.

BetterYou Vitamin D1000 Spray: best spray

A peppermint spray giving 25mcg per spray and 100 doses, about 7p a day. Ideal if you struggle with capsules. Caveat: the "absorbed through the mouth" claim is the brand's; the real advantage is convenience. Check the label for the D3 source if you are vegan.

Together Health Vitamin D3: best vegan capsule in oil

25mcg vegan D3 from lichen in coconut oil. Vitamin D is fat-soluble, so taking it with fat or a meal helps absorption. Caveat: like the others, it is above the NHS baseline and has no published third-party test.

Viridian Vitamin D3 & K2: best moderate D3 and K2

If you have decided you want K2, this pairs 25mcg D3 with a modest 45mcg K2 (MK-7). Caveat: the K2 evidence is weak (see below), it is much pricier than plain D3, and vitamin K can interfere with warfarin.

Puresport 4000IU D3 + K2: best tested option for athletes

The only vitamin D we found with Informed Sport certification on the product page, using vegan D3 from algae. Useful for competitive athletes who need batch screening. Caveat: at 100mcg D3 it is at the NHS maximum on its own. Most people should not take this daily without medical advice.

Bare Biology Beam & Balance: high-dose vegan spray

Three sprays give 100mcg D3 and 100mcg K2. Because it is a spray, you can take one spray instead of three. Caveat: the full serving is at the NHS upper limit, and the page does not clearly state the dose per single spray.

What does the evidence say about vitamin D?

The case for taking it

Low vitamin D can lead to bone pain and soft bones (osteomalacia) in adults and rickets in children. In the UK, the short winter days make low levels common, which is why the NHS advice exists. This is the main, well-supported reason to take a supplement.

What vitamin D does not seem to do

The VITAL trial gave 25,871 US adults 2,000 IU a day or a placebo for about five years and found no drop in invasive cancer or major heart events. A 2026 meta-analysis of nine trials and over 114,000 people reached the same conclusion for heart disease. A Cochrane review found D3 seemed to reduce deaths in older people living independently or in care, but noted weaknesses in the evidence and more kidney stones when D3 was combined with calcium. In short, more is not better once you are not deficient.

Is K2 worth adding?

K2 (menaquinone) helps activate proteins involved in putting calcium into bone. The idea that it "steers calcium away from arteries" is plausible but unproven. A systematic review of trials found vitamin K did not consistently slow artery calcification or stiffening, and a Cochrane review found too little evidence to draw conclusions. The NHS says 1mg or less of vitamin K a day from supplements is unlikely to cause harm, so the doses in these products are well within that, but K2 adds cost without a proven benefit.

Who should be careful?

• People on warfarin or similar blood thinners: avoid K2 products unless your anticoagulation clinic agrees. Vitamin K directly affects how these drugs work.
• People with kidney disease, sarcoidosis or high calcium: speak to your GP before taking vitamin D.
• Anyone taking several supplements: add up the vitamin D from multivitamins, fish oils with D, and fortified foods.
• Children: use products made for their age group; the NHS has separate advice for babies and children.

What to avoid

• 4,000 IU daily products as a default "for immunity". They sit at the upper limit and big trials do not show extra benefit.
• Weekly "mega-doses" unless prescribed.
• Paying a premium for K2 on the promise of heart protection.

Bottom line

For most UK adults the best vitamin D supplement is the simplest: 10mcg of D3 a day from October to March, or all year if you get little sun or have dark skin. Viridian's 400iu capsules match that exactly; Vitl's tin and BetterYou's spray are cheap 25mcg options. Skip high-dose and K2 combinations unless a clinician has a specific reason for them.