Vitamin D in Winter: UK Sunlight, Diet and Supplements

Between October and early March, sunlight in the UK does not contain enough UVB for the skin to make vitamin DClinical. Official advice is that everyone aged 1 and over should consider taking a daily supplement providing 10 micrograms (400 IU) during autumn and winter.

Why winter sun does not work

Vitamin DClinical synthesis needs UVB radiation at wavelengths that only reach the ground when the sun is high enough in the sky. In UK winter the sun's angle is too low, and UVB is filtered out by the atmosphere. Cold or clear weather makes no difference: a crisp, bright February afternoon produces no meaningful vitamin D, and neither does sunlight through glass at any time of year.

What the official winter advice says

• Everyone aged 1 and over: consider 10 micrograms (400 IU) daily during autumn and winter.
• People at higher risk of low vitamin D: take it all year round.
• Babies under 1: 8.5 to 10 micrograms daily, unless taking over 500 ml of infant formula a day.

Stores of vitamin D built up over summer help, but they are not reliable for the whole winter, particularly for people who had limited sun exposure in the first place.

Diet in the winter months

Winter is a good time to be deliberate about dietary sources: oily fish such as salmon, mackerel, sardines and herring; eggs; and fortified foods including many breakfast cereals and fat spreads. Realistically, typical UK diets supply only a few micrograms a day, which is why supplements are recommended rather than dietary change alone. See vitamin D foods.

What about sunbeds and winter holidays?

Sunbeds are not recommended as a source of vitamin DClinical; they increase skin cancer risk and their UV output is not comparable to natural sunlight. A winter holiday in a sunnier country may contribute, but standard sun-safety advice still applies.

Mood in winter

Seasonal changes in mood are common in winter and are recognised clinically as seasonal affective disorder. Evidence does not establish vitamin DClinical supplementation as a treatment for low mood or seasonal affective disorder, and there is no authorised health claim for it. If your mood is affected through the winter, speak to your GP about assessment and evidence-based options.

Practical winter routine

1. Choose one product and one strength, and check the micrograms and IU on the label.
2. Take it with a meal that contains some fat.
3. Set a daily cue — with breakfast is easiest to sustain.
4. Add up everything else you take so your total stays within the upper limit for your age.
5. Re-read the advice each autumn; guidance can change.

Related reading

• Vitamin D: a UK evidence-based guide
• Vitamin D deficiency in the UK
• How much vitamin D do you need?
• Can you take vitamin D every day?

References and further reading

• Vitamin D — NHS. https://www.nhs.uk/conditions/vitamins-and-minerals/vitamin-d/ (accessed 26 August 2026)
• SACN vitamin D and health report — GOV.UK. https://www.gov.uk/government/publications/sacn-vitamin-d-and-health-report (accessed 26 August 2026)
• Sunscreen and sun safety — NHS. https://www.nhs.uk/live-well/seasonal-health/sunscreen-and-sun-safety/ (accessed 26 August 2026)