Best Vitamin D Supplement UK: How to Choose (D3, Dose and Format)

By the GUUDIES Editorial Team · Updated 26 October 2026 · Health claims checked against the GB Nutrition and Health Claims Register (sources below).

Disclosure: GUUDIES makes a daily gummy pouch that contains vitamin D3, so we have an interest here. We have kept to what NHS guidance and the evidence say, and linked our sources.

What is the best vitamin D supplement in the UK? For most adults, the best vitamin D supplement is one that gives vitamin D3 (cholecalciferol) at around 10µg (400 IU) a day or a little more, stays well under the NHS upper limit of 100µg (4,000 IU), and comes in a format you will actually take every day from October to March. The brand matters far less than the form, the dose and taking it consistently with food.

Why Almost Everyone in the UK Needs to Think About Vitamin D

Your skin makes vitamin D when UVB light hits it. At British latitudes the sun sits too low between October and early March for useful UVB to reach the ground, so skin makes little or none in those months, whatever the weather. Glass blocks UVB too, so sitting by a sunny window does not help.

That is why the NHS advises that adults and children over 4 consider taking 10 micrograms of vitamin D a day during autumn and winter. It also suggests some people consider taking it all year round:

• people who are not often outdoors, such as those who are frail or housebound
• people who usually wear clothes that cover most of their skin when outside
• people with dark skin, for example those of African, African-Caribbean or South Asian background

How to Choose the Best Vitamin D Supplement: 6 Checks

1. Choose D3 over D2

Vitamin D comes as D3 (cholecalciferol) or D2 (ergocalciferol). A 2012 meta-analysis in the American Journal of Clinical Nutrition found D3 was more effective than D2 at raising blood levels of vitamin D. Most UK supplements now use D3, but cheaper products and some plant-based ones still use D2, so check the label.

2. Check the dose, and convert IU to micrograms

Labels use micrograms (µg) or international units (IU), sometimes both. 1µg = 40 IU.

Micrograms	IU	What it means
10µg	400 IU	The NHS daily amount for adults in autumn and winter
20µg	800 IU	A common UK supplement dose
25µg	1,000 IU	Common in "1,000 IU" products
100µg	4,000 IU	The NHS upper limit for adults; do not go above this

A 1,000 IU product sounds much bigger than a 20µg one, but it is only slightly more. Convert before you compare.

3. Stay under the upper limit

Vitamin D is fat soluble and is stored in the body, so more is not better. The NHS says adults should not take more than 100µg (4,000 IU) a day, and children aged 1 to 10 no more than 50µg (2,000 IU). Add up everything you take: a multivitamin, a separate vitamin D and any fortified drinks all count. If your GP has prescribed a higher dose, follow their advice.

4. Pick a format you will take every day

Format	Good for	Watch out for
Tablets and softgels	Low cost, many dose options	Easy to forget; some people dislike swallowing pills
Oral sprays	No swallowing, quick	Dose per spray is small; check how many sprays you need
Drops	Flexible dosing, children's products	Measuring drops accurately
Gummies	Pleasant to take, easy habit	Sugar per gummy; gelatine in many brands

The research on vitamin D is about daily intake over months, so the format you will stick with is the right one for you.

5. Check it suits your diet

Standard D3 usually comes from lanolin (sheep's wool grease), which is vegetarian but not vegan. Vegans should look for D3 from lichen or for a product labelled vegan. In gummies, check for pectin rather than gelatine.

6. Look at what comes with it

Many products pair vitamin D with vitamin K2. That is fine for most people, but vitamin K interacts with warfarin and some other anticoagulants. If you take a blood thinner, speak to your GP or anticoagulation clinic before taking anything containing vitamin K.

What Vitamin D Does

These are the authorised UK health claims for vitamin D:

• Vitamin D contributes to the normal function of the immune system.
• Vitamin D contributes to the maintenance of normal bones, teeth and muscle function.
• Vitamin D contributes to normal absorption and use of calcium and phosphorus.

Claims beyond these, such as preventing colds, depression or weight gain, are not authorised in the UK.

When and How to Take Vitamin D

• With food. Vitamin D is fat soluble, so take it with a meal that contains some fat.
• Every day. Consistency matters more than the time of day.
• October to March at least. All year if you are in one of the NHS groups above.

Can You Get Enough Vitamin D From Food?

Oily fish (salmon, mackerel, sardines, herring), egg yolks, red meat and liver contain some, and many breakfast cereals, fat spreads and plant drinks are fortified. Very few foods contain much naturally, so food alone rarely covers the winter gap. That is the reason vitamin D is the one supplement UK public health guidance recommends to the whole population.

Do You Need a Blood Test First?

Most people do not need a test to follow the NHS 10µg advice. If you have symptoms such as ongoing bone pain or muscle weakness, or you are in a high-risk group, ask your GP. Our guide to the vitamin D blood test in the UK explains the options.

Where GUUDIES Fits

The Daily Greens+ gummy in each GUUDIES pouch contains 20µg (800 IU) of vitamin D3 (cholecalciferol), alongside 80µg of vitamin K2 and twelve other vitamins and minerals. It is pectin based and vegan, with about 0.4g of sugar per gummy. If you already take a separate vitamin D, add the two together and keep your total under 100µg a day.

Five of the six gummies in the pouch are vegan; the Marine Collagen gummy contains fish collagen. See what is in a GUUDIES pouch.

Common Questions

What is the best vitamin D supplement in the UK?
One that provides vitamin D3 at about 10µg (400 IU) a day or a little more, stays under 100µg a day, suits your diet, and comes in a format you will take every day with food.

How much vitamin D should I take a day in the UK?
The NHS advises 10 micrograms (400 IU) a day for adults and children over 4 in autumn and winter, and says adults should not take more than 100 micrograms (4,000 IU) a day.

Is D3 better than D2?
Research suggests D3 raises blood vitamin D levels more effectively than D2, which is why most UK supplements use D3.

Is 1,000 IU of vitamin D too much?
1,000 IU is 25 micrograms, which is well under the NHS adult upper limit of 100 micrograms a day.

Are vitamin D gummies as good as tablets?
If the gummy declares its dose and you take it daily, it can supply the same vitamin D as a tablet. Check the sugar content and whether it uses gelatine.

Is vitamin D3 vegan?
Only if it comes from lichen or is labelled vegan. Standard D3 comes from lanolin, from sheep's wool.

When is the best time to take vitamin D?
With a meal that contains some fat, at whatever time of day helps you remember it.

Sources

• NHS, Vitamin D: nhs.uk
• Tripkovic L et al. Comparison of vitamin D2 and vitamin D3 supplementation in raising serum 25-hydroxyvitamin D status. Am J Clin Nutr 2012: PubMed
• GB Nutrition and Health Claims Register: gov.uk

This article is general information, not medical advice. Food supplements should not be used as a substitute for a varied, balanced diet and a healthy lifestyle.

Related Reading

How Much Vitamin D Should I Take? · Vitamin D Deficiency Symptoms · Vegan Vitamin D Gummies · Vitamin D3 in GUUDIES · See our full ingredient list