Last updated: October 2026
Vitamin D is the umbrella name. Vitamin D3 (cholecalciferol) is the form your skin makes in sunlight and the one most supplements use. Vitamin D2 (ergocalciferol) comes from fungi and yeast. Studies suggest D3 raises blood levels more than D2. D3 can be vegan, made from lichen or algae. The NHS advises 10 micrograms a day from October to March.
Below: D2 vs D3 side by side, vegan D3, whether you need K2, how much to take, who needs it most and what vitamin D actually does.
The short version: pick vitamin D3, take 10 micrograms (400 IU) a day from October to March with a meal, and choose lichen or algae D3 if you’re vegan. K2 is optional, not essential, and not for anyone on warfarin.
Is vitamin D the same as D3?
Not quite. “Vitamin D” is a family name that covers two main forms you’ll see on labels:
- Vitamin D3 (cholecalciferol, spelt colecalciferol by the NHS): the type your skin makes when sunlight hits it, and the type found in oily fish, eggs and most supplements.
- Vitamin D2 (ergocalciferol): made by fungi and yeast exposed to UV light, and used in some fortified foods and prescription products.
So a tub labelled “vitamin D” will usually contain D3, but not always. Turn the pack over: the ingredients list will say cholecalciferol (D3) or ergocalciferol (D2).
Both forms are inactive when you take them. Your liver turns them into 25-hydroxyvitamin D, which is what a blood test measures, and your kidneys then make the active form your body uses. If you’ve ever had a vitamin D test, the result covers D2 and D3 together. For what a low result looks like, see vitamin D deficiency symptoms.
D2 vs D3: which is better?
| Vitamin D2 (ergocalciferol) | Vitamin D3 (cholecalciferol) | |
|---|---|---|
| Where it comes from | Fungi and yeast exposed to UV light | Made in your skin; supplements use lanolin (sheep’s wool), lichen or algae |
| Vegan? | Yes | Only if made from lichen or algae |
| Raising blood levels | Works, but less well in head-to-head trials | More effective in most trials, including a UK study at everyday doses |
| In food | Some fortified foods and UV-treated mushrooms | Oily fish, egg yolks, red meat, liver, some fortified foods |
| Typical UK supplements | Less common; some vegan products and prescription items | Most high street tablets, sprays, drops and gummies |
For most people, D3 is the better choice. A 2012 meta-analysis of randomised trials led by the University of Surrey found D3 raised blood levels of vitamin D more than D2. The gap was clearest with large, occasional doses and much smaller with daily doses.
A later Surrey trial settled the daily question for UK conditions. In 335 South Asian and white European women given 15 micrograms a day through the winter, in juice or biscuits, D3 raised blood levels clearly more than D2. The British Dietetic Association says the same in plain words: D3 is the most effective, and D2 is a plant-based alternative for vegetarians and vegans.
That doesn’t make D2 useless. If D2 is what you have, it still provides vitamin D. But if you’re choosing, choose D3.
Vegan vitamin D3: lichen and algae
Most D3 in supplements is made from lanolin, the grease in sheep’s wool, so it isn’t vegan. That’s why vegans were once told to stick to D2.
You no longer have to. The Vegan Society notes that vegan D3 can be made from lichen, a partnership of fungus and algae, and D3 from algae is now available too. You get the better-performing form without any animal source.
When you shop, check three things:
- The form: cholecalciferol (D3) from lichen or algae, often marked with a vegan logo.
- The capsule: softgels are often gelatine, which isn’t vegan. Tablets, drops, sprays or plant-based capsules avoid it.
- The amount: 10 micrograms (400 IU) matches NHS advice. Higher strengths are fine within the limit, but more isn’t better.
Our Evolabs Mint CBD Oil with vitamin D3 uses vegan, algae-based D3 in a broad spectrum CBD oil with 0% THC. Vitamin D contributes to the normal function of the immune system. Check the label for the amount of D3 per serving and count it towards your daily total if you also take a separate vitamin D. You can read why we chose algae-based D3 and whether CBD oil is vegan in general.
The FSA’s 10mg a day figure is precautionary advice rather than a legal limit, set while longer-term safety research continues. At Evopure we think it is a very cautious figure, and many adults use more. If you go above it, increase slowly, and check with your GP or pharmacist first if you take any medication.
Our products are for adults (18+) only. We don’t recommend our products during pregnancy or breastfeeding.
Should you take vitamin D3 with K2?
For most people, no: it’s optional. The NHS doesn’t advise taking K2 alongside vitamin D, and says you should be able to get all the vitamin K you need from a varied diet.
What K2 is. Vitamin K comes in two main forms. K1 (phylloquinone) is in green leafy vegetables such as broccoli and spinach, vegetable oils and cereal grains. K2 (menaquinones, such as MK-7) is made by bacteria and found in fermented foods and some animal foods. Vitamin K contributes to normal blood clotting and to the maintenance of normal bones.
The theory. Vitamin D contributes to normal absorption/utilisation of calcium and phosphorus, and vitamin K activates proteins that handle calcium in bone and blood vessels. So the pairing is sold as getting calcium “to the right place”.
What the evidence shows. It’s thinner than the marketing suggests:
- A 2019 UK-led review of 36 vitamin K trials found no evidence that it changed bone density or spine fractures in post-menopausal women or people with osteoporosis. It might reduce other fractures, but the evidence wasn’t strong enough to say.
- A Danish trial gave 365 men with heart valve calcification 720 micrograms of MK-7 plus 25 micrograms of vitamin D, or a placebo, for two years. Calcification progressed the same in both groups.
- A 2024 review of 31 studies of vitamin D with vitamin K in post-menopausal women reported some positive findings for bone and heart markers, but the trials varied widely in doses, forms and length.
Our honest take: D3 with K2 is a reasonable personal choice if you’re healthy, not on blood thinners, and prefer a combined product. It isn’t something you need just because you take vitamin D3. If you take D with other supplements, see magnesium and vitamin D and magnesium and calcium together.
Who should avoid K2
Vitamin K directly affects blood clotting, so it can undo the effect of some blood-thinning medicines.
- Warfarin and other vitamin K antagonists: the NHS says not to take vitamin K supplements while you’re on warfarin. In a small study of healthy volunteers given a similar blood thinner, as little as 10 micrograms of MK-7 a day noticeably changed its effect in some of them.
- Any other anticoagulant, or a heart, liver or kidney condition: ask your GP, pharmacist or anticoagulant clinic before taking a D3 and K2 product.
- High doses: the NHS says 1mg (1,000 micrograms) or less of vitamin K supplements a day is unlikely to cause harm, and there isn’t enough evidence on the effects of higher doses.
Many combined D3 and K2 products and multivitamins contain vitamin K, so check every label if you’re on warfarin. See are multivitamins worth taking?
How much vitamin D3 to take
The NHS advises everyone in the UK, including pregnant and breastfeeding women, to consider 10 micrograms of vitamin D a day in autumn and winter. That figure comes from the Scientific Advisory Committee on Nutrition’s 2016 review, which set 10 micrograms a day as the reference intake for everyone aged 4 and over.
- Upper limit for adults: no more than 100 micrograms (4,000 IU) a day, unless a doctor has advised more. Taking too much over a long time can cause calcium to build up in the body.
- Children: amounts and limits are lower and differ by age. Follow the NHS vitamin D guidance for babies and children. Our products are for adults only.
- Sunlight: you can’t overdose on vitamin D from the sun, but from October to March UK sunlight isn’t strong enough to make much.
Take it with a meal that contains some fat, at whatever time of day you’ll remember. For morning vs night, see the best time to take vitamin D. For the winter picture in full, see vitamin D in winter.
Micrograms vs IU
Labels use micrograms (µg or mcg), international units (IU), or both. The NHS conversion is simple: 1 microgram equals 40 IU.
| Micrograms | IU | What it means |
|---|---|---|
| 10 micrograms | 400 IU | The NHS daily amount |
| 25 micrograms | 1,000 IU | A common “high strength” tablet |
| 50 micrograms | 2,000 IU | Higher strength |
| 100 micrograms | 4,000 IU | The daily upper limit for adults |
Add up every source: a vitamin D tablet, a multivitamin and fortified drinks or oils can stack up quickly.
Who needs vitamin D most
The NHS says these adults should take 10 micrograms every day all year round, not just in winter:
- people who are rarely outdoors, such as those who are frail or housebound
- people living in a care home
- people who usually cover most of their skin when outdoors
People with dark skin, such as those of African, African-Caribbean or South Asian background, may also not make enough from sunlight and should consider a supplement all year. The British Dietetic Association adds people over 65 to the higher-risk list.
Short days, less daylight and poor sleep are common reasons for feeling tired in the darker months, and low vitamin D is worth ruling out. See why you’re tired in winter, why am I always tired? and seasonal affective disorder. If you think you’re low, your GP can arrange a blood test.
What vitamin D does
These are the authorised health claims for vitamin D in Great Britain, in their official wording:
- Vitamin D contributes to the maintenance of normal bones.
- Vitamin D contributes to the maintenance of normal teeth.
- Vitamin D contributes to the maintenance of normal muscle function.
- Vitamin D contributes to the normal function of the immune system.
- Vitamin D contributes to normal absorption/utilisation of calcium and phosphorus.
- Vitamin D contributes to normal blood calcium levels.
D2 and D3 are both vitamin D, so these apply to either form. Be wary of any product promising more, such as better mood or weight loss. For the wider picture on bones and immunity, see calcium supplements, magnesium and bone health and how to support your immune system.
FAQs
Is vitamin D3 the same as vitamin D?
Vitamin D3 is one form of vitamin D. “Vitamin D” covers both D2 and D3, but most supplements labelled vitamin D contain D3 (cholecalciferol).
Is vitamin D2 or D3 better?
D3 is generally better. Trials, including a UK study using 15 micrograms a day in winter, found D3 raised blood levels of vitamin D more than D2.
Is vitamin D3 vegan?
Only if it’s made from lichen or algae. Most D3 comes from lanolin in sheep’s wool, which isn’t vegan. Check the label and the capsule, as softgels are often gelatine.
Do I need to take K2 with vitamin D3?
No. The NHS doesn’t advise it, and trials of the pairing are mixed. Most people get enough vitamin K from a varied diet. Never take vitamin K supplements if you’re on warfarin.
How many IU is 10 micrograms of vitamin D?
10 micrograms is 400 IU. One microgram equals 40 IU, so the adult upper limit of 100 micrograms is 4,000 IU.
Can I take vitamin D3 if I’m on warfarin?
Plain vitamin D3 doesn’t contain vitamin K, but check with your pharmacist or anticoagulant clinic before starting any supplement, and avoid D3 and K2 combinations.
Sources
- NHS. Vitamin D and Vitamin K.
- NHS. Warfarin.
- Scientific Advisory Committee on Nutrition (2016). Vitamin D and health report. GOV.UK.
- Department of Health and Social Care. Great Britain nutrition and health claims (NHC) register. GOV.UK.
- British Dietetic Association. Vitamin D: food fact sheet.
- The Vegan Society. Vitamin D.
- Tripkovic L et al (2012). Comparison of vitamin D2 and vitamin D3 supplementation in raising serum 25-hydroxyvitamin D status: a systematic review and meta-analysis. American Journal of Clinical Nutrition.
- Tripkovic L et al (2017). Daily supplementation with 15 μg vitamin D2 compared with vitamin D3 to increase wintertime 25-hydroxyvitamin D status in healthy South Asian and white European women. American Journal of Clinical Nutrition.
- Mott A et al (2019). Effect of vitamin K on bone mineral density and fractures in adults: an updated systematic review and meta-analysis of randomised controlled trials. Osteoporosis International.
- Diederichsen ACP et al (2022). Vitamin K2 and D in patients with aortic valve calcification: a randomized double-blinded clinical trial. Circulation.
- Rusu ME et al (2024). Investigating the effects and mechanisms of combined vitamin D and K supplementation in postmenopausal women: an up-to-date comprehensive review of clinical studies. Nutrients.
- Theuwissen E et al (2013). Effect of low-dose supplements of menaquinone-7 (vitamin K2) on the stability of oral anticoagulant treatment. Journal of Thrombosis and Haemostasis.
This guide is general information, not medical advice. Evopure makes the Evolabs Mint CBD Oil with vitamin D3.
