Do you need vitamin D in winter? If you live in the UK, almost certainly yes. From October to March the sun isn't strong enough for your skin to make enough, so UK guidance says to consider 10 micrograms a day. And if you already take it, it's worth checking whether it's D2 or D3.
Because once the clocks go back and it's dark by 4pm, that extra hour in bed is about the only thing winter gives us for free.
The quick version
- From October to March, adults and children over four in the UK should consider 10 micrograms of vitamin D a day.
- Vitamin D contributes to the maintenance of normal bones, teeth and muscle function, and to the normal function of the immune system.
- D2 and D3 both count, but a research review found taking D2 lowered blood levels of D3.
- Check your label for "D3" or "cholecalciferol".
Do you need vitamin D in winter in the UK?
Your body makes most of its vitamin D from sunlight on your skin. The catch is that in the UK, from October to March, the sun just isn't strong enough for that to happen properly.
That's why the government's scientific advisers recommend 10 micrograms a day (SACN, 2016), and the NHS advises considering a supplement through autumn and winter (NHS).
Some people are advised to take it all year round, including people who aren't often outdoors, usually cover most of their skin, or have darker skin.
What does vitamin D actually do?
Quite a lot. Vitamin D contributes to:
- the maintenance of normal bones and teeth
- the maintenance of normal muscle function
- the normal function of the immune system
Not bad for something most of us forget about until spring.
Vitamin D2 vs D3: what's the difference?
Vitamin D2 and D3 both count towards your vitamin D status, but they're not identical. A University of Surrey review found people taking D2 had lower blood levels of D3 than those who didn't take it. D3, often listed as cholecalciferol, is the form your skin makes from sunlight.
D2 (ergocalciferol) is usually made from yeast or mushrooms. In the review, taking it was linked to a drop in D3 levels of roughly 9 to 18 nmol/L (Brown et al., 2025). D2 still adds to your overall vitamin D, and the researchers say bigger studies are needed. But it's a good reason to read the small print.
Most people never check which form they're taking. Now's a good time to start.
Not sure if you're getting enough vitamin D? Take the ALYVE quiz. Our personalised formulas use vitamin D3, sourced from lichen, so they're vegan-friendly too.
Can you get enough vitamin D from food?
It's tricky. Oily fish, red meat, egg yolks and some fortified cereals and spreads all contain vitamin D, but the NHS says it's difficult to get enough from food alone. So unless you're eating salmon for breakfast, lunch and dinner, a supplement makes life easier.
How much vitamin D is too much?
More isn't better. The NHS advises adults not to take more than 100 micrograms a day, as it could be harmful. If you're pregnant, taking medication or managing a health condition, speak to your GP or pharmacist before starting a supplement.
Your three-step winter reset
Check your label. Look for "D3" or "cholecalciferol" rather than "D2" or "ergocalciferol".
Chase the daylight. A lunchtime walk or a coffee by the window is one of the easiest wins when the evenings are dark. My tips on adjusting your sleep when the clocks change help too.
Keep your routine steady. Darker evenings make it very tempting to let sleep, meals and movement drift. Keep a few anchors, like the same wake-up time and regular meals, and winter feels a lot less chaotic.
The clocks are going back. Your routine doesn't have to.
Want a formula built around you, not the average person? Take the ALYVE quiz, or book a call with one of our nutritionists.
Frequently asked questions
When should I take vitamin D in the UK?
UK guidance says adults and children over four should consider 10 micrograms a day from October to March. Some people, such as those who are rarely outdoors or have darker skin, are advised to take it all year.
Is vitamin D3 better than D2?
Both count towards your vitamin D status. A University of Surrey review found taking D2 lowered blood levels of D3, but more research is needed to know what that means for health.
How do I know if my supplement is D2 or D3?
Check the label. D3 is often listed as cholecalciferol, and D2 as ergocalciferol.
Can you get vitamin D from the sun in winter in the UK?
Not really. From October to March the sun isn't strong enough for your skin to make enough vitamin D.
References
Brown, E. et al. (2025). Effect of vitamin D2 supplementation on 25-hydroxyvitamin D3 status: a systematic review and meta-analysis of randomized controlled trials. Nutrition Reviews. Available at: https://doi.org/10.1093/nutrit/nuaf166
NHS. Vitamin D. Available at: https://www.nhs.uk/conditions/vitamins-and-minerals/vitamin-d/
Scientific Advisory Committee on Nutrition (2016). Vitamin D and Health. London: Public Health England. Available at: https://assets.publishing.service.gov.uk/media/5a804e36ed915d74e622dafa/SACN_Vitamin_D_and_Health_report.pdf
