Quick answer
- The NHS advises everyone to consider 10 µg (400 IU) a day from October to March, all year if you are rarely outdoors, cover your skin or have dark skin. Adults should not take more than 100 µg (4,000 IU) a day.
- Choose vitamin D3 (cholecalciferol): it raises blood levels more effectively than D2. Vegan D3 from lichen exists.
- Elsewhere in Europe: EFSA's adequate intake is 15 µg (600 IU) a day; Germany's BfR recommends no more than 20 µg (800 IU) per daily dose in a supplement; Spain sets no national maximum.
- Vitamin D does not need K2 to work, and there is no authorised claim for the combination.
Key numbers
- UK daily amount (NHS)
- 10 µg (400 IU)/day
- From age 1; a supplement is advised October to March.
- UK maximum (NHS)
- 100 µg (4,000 IU)/day
- Adults and ages 11–17; 50 µg for ages 1–10, 25 µg under 1.
- Adequate intake, adults (EFSA)
- 15 µg (600 IU)/day
- Safe upper level (EFSA)
- 100 µg (4,000 IU)/day
- All sources together.
- Germany (BfR guidance)
- 20 µg (800 IU) per daily dose
- Spain
- No national maximum
- Reference intake on UK and EU labels (NRV)
- 5 µg (200 IU)
- That is why 20 µg shows as 400% NRV.
- Conversion
- 1 µg = 40 IU
What these terms mean: NRV upper levels (NHS, EFSA) maximum levels by country daily dose
How to choose
- Check the dose per daily serving in µg: 10 µg (400 IU) is the NHS amount, and 10–25 µg a day covers most adults in winter. Weekly or monthly mega-doses are not advised.
- Pick D3. If you are vegan, look for D3 from lichen.
- Take it with a meal that contains some fat, or choose drops or softgels in oil.
- Count vitamin D from other products: multivitamins, fortified foods and omega-3 with added D all add up.
- Only add K2 if you want it for another reason, and never if you take a coumarin-type blood thinner such as warfarin.
Vitamin D forms compared
| Form | What it is | Good to know |
|---|---|---|
| D3 (cholecalciferol) | The form your skin makes; usually from lanolin (sheep’s wool) | Raises blood levels more than D2 |
| Vegan D3 | D3 made from lichen | Same molecule, suitable for vegans |
| D2 (ergocalciferol) | Plant or fungal origin | Less effective at raising blood levels |
| Drops in oil | D3 dissolved in oil | Easy to adjust; check µg per drop |
| D3 + K2 | Combination with menaquinone (MK-7) | No authorised claim for the combination |
Maximum vitamin D per day, by country
The NHS advises 10 µg a day in autumn and winter and no more than 100 µg (4,000 IU) a day from supplements. Other countries draw the line much lower: a 100 µg tablet is five times the German and Austrian guidance and above every binding limit in the table.
Limits are per recommended daily dose of a supplement, for adults; several countries set lower ones for children and teenagers. Inside the EU, a product lawfully sold in one country can usually be sold in another even above its limit (mutual recognition). All 7 nutrients and 13 countries →
What the evidence says
Your skin makes vitamin D from sunlight, but between roughly October and March the sun in the UK and most of Europe is too weak for that. In the UK national diet survey, 29% of adults were below 25 nmol/l in January to March; in Germany’s national health survey, 61.6% of adults were below 50 nmol/l (a stricter threshold), and in Spain levels were clearly lower after winter than after summer. Older people, people with darker skin and people who rarely get sun are most at risk.
A daily supplement corrects low levels reliably. Whether it does much more than that in people who are not low is far less clear. Read vitamin D in a European winter for who needs it, and D3 with K2 before paying extra for a combination.
What the label may legally claim
Authorised claims (GB and EU registers)
- Contributes to normal function of the immune system
- Contributes to the maintenance of normal bones, teeth and muscle function
- Contributes to normal absorption and use of calcium and phosphorus, and to normal blood calcium levels (all from 0.75 µg per daily dose)
Not authorised in GB or the EU
- Better mood or beating the winter blues
- Preventing colds or flu
- More energy
How health claims work (UK & EU): health claims
Products we have checked
Label data checked by NutriMetrics for products sold in Spain and Germany. UK product checks are next. Sorted alphabetically, not ranked.
| Product | Per daily dose | Sold in | Label |
|---|---|---|---|
| Solgar Vitamin D3 2200 IU (55 µg)1 capsule a day | Vitamin D3: 55 µg | Spain (not yet confirmed) · Germany (not yet confirmed) | Source |
| Vita Natura Vitamin D3+K2 1000 IE Tropfen1 drop a day | Vitamin D3: 25 µg Vitamin K2 (MK-7): 20 µg · all-trans MK-7 | Germany | Source |
Who should be careful
- More than 100 µg a day: the NHS says this could be harmful for adults; for children aged 1 to 10 the limit is 50 µg. Follow your GP if they prescribe a different dose.
- High doses taken every few days or weeks: Germany's BfR advises against them; take a moderate daily dose instead.
- Blood thinners: products with K2 can weaken coumarin-type anticoagulants such as warfarin.
- Kidney disease, sarcoidosis or high blood calcium: take vitamin D only with medical advice.
FAQ
How much vitamin D should I take a day?
In the UK, the NHS advises 10 µg (400 IU) a day in autumn and winter, and all year for people at higher risk. Do not take more than 100 µg a day. EFSA's adequate intake is 15 µg a day. A 25(OH)D blood test is the only way to know if you are low.
Is vitamin D3 better than D2?
Yes, for raising blood levels. A meta-analysis found D3 more effective than D2 at increasing serum 25(OH)D.
Do I need vitamin K2 with vitamin D?
No. Vitamin D works without K2, the NHS advises plain vitamin D, and there is no authorised claim for the combination in the UK or the EU. K2 can interfere with some blood thinners.
Is 4,000 IU a day too much?
4,000 IU (100 µg) is the most the NHS says adults should take a day, and EFSA's safe upper level for total intake. It is a ceiling, not a target: ten times the NHS daily amount, five times Germany's guidance for a single supplement and above the legal limit in several EU countries.
Sources
- SACN — Fortifying foods and drinks with vitamin D (NDNS vitamin D status)
- NHS — Vitamin D
- SACN (2016) — Vitamin D and health
- DHSC — Great Britain nutrition and health claims (NHC) register
- European Commission — EU Register of nutrition and health claims
- EFSA (2023) — Scientific opinion on the tolerable upper intake level for vitamin D
- EFSA — Dietary reference values
- BfR — Recommended maximum levels for vitamins and minerals in food supplements
- BfR — High single doses of vitamin D taken days or weeks apart carry health risks
- Tripkovic L et al. Comparison of vitamin D2 and vitamin D3 supplementation. Am J Clin Nutr, 2012
- NIH Office of Dietary Supplements — Vitamin D fact sheet for health professionals
Information only, not medical advice. No product on this page is a paid placement.