Guide
Vitamin D for women through the year: how much, when and why
The NHS advises UK adults consider a daily 10 microgram (400 IU) vitamin D supplement in autumn and winter, when sunlight is too weak for the skin to make enough. Some people, including those with dark skin or little sun exposure, are advised to take it all year. The same 10 micrograms applies in pregnancy and breastfeeding. Do not exceed 100 micrograms a day without clinical advice.
Why vitamin D matters for women
Vitamin D helps the body absorb calcium and keep bones, teeth and muscles healthy. EFSA recognises that vitamin D contributes to the maintenance of normal bones, to normal muscle function, to the normal absorption and use of calcium, and to the normal function of the immune system. For women this matters across life: it supports the developing baby's bones in pregnancy, and it becomes more important after menopause, when lower oestrogen is associated with faster bone loss.
Why autumn and winter are the key months
Most vitamin D is made in the skin from summer sunlight. From about October to March in the UK, the sun is too low in the sky for the skin to make vitamin D, so stores built up over summer have to last. This is why the NHS advises that everyone consider a daily 10 microgram supplement during autumn and winter. In spring and summer, most people make enough from short, regular periods of sun exposure and from food.
Who should take it all year
- People who are not often outdoors, for example those who are frail or housebound.
- People who usually wear clothes that cover most of their skin outdoors.
- People with dark skin, for example of African, African-Caribbean or south Asian background.
- Women who are pregnant or breastfeeding, who are advised 10 micrograms daily throughout.
How much, and the upper limit
The advised supplement amount is 10 micrograms (400 IU) a day for adults. The NHS sets an upper limit of 100 micrograms (4,000 IU) a day for adults, including pregnant and breastfeeding women, unless a clinician advises more. Taking very high amounts over a long time can cause too much calcium in the body, which can damage bones, kidneys and the heart, so more is not better.
How to compare products
- Check both units: 10 micrograms equals 400 IU, so a "1000 IU" product provides 25 micrograms.
- Look at the form: D3 is most commonly recommended; vegan D3 from lichen exists if you avoid lanolin-derived D3.
- Decide on format: tablets, softgels and oral sprays all work; pick what you will actually take.
- Price it by the active amount, not the bottle size. Our cost per effective dose tool works out the price per 10 micrograms.
Compare brands
See our roundup of the best vitamin D in the UK, the full vitamin D pillar, and the question many ask, how much vitamin D do I need.
Sources
- NHS: Vitamin D (nhs.uk/conditions/vitamins-and-minerals/vitamin-d/)
- NHS: Vitamins and minerals overview (nhs.uk/conditions/vitamins-and-minerals/)
- EFSA authorised health claims register (Regulation (EU) 432/2012, retained in GB law)
Frequently asked questions
How much vitamin D should women take?
The NHS advises adults consider a daily supplement containing 10 micrograms (400 IU) of vitamin D, particularly in autumn and winter. The same 10 microgram amount applies during pregnancy and breastfeeding. Do not take more than 100 micrograms (4,000 IU) a day unless a clinician advises it.
Who should take vitamin D all year round?
The NHS advises year-round supplementation for people who get little sun on their skin, such as those who are housebound, usually cover up outdoors, or are in an institution; and for people with dark skin, for example of African, African-Caribbean or south Asian background, who may not make enough vitamin D from sunlight even in summer.
Is vitamin D3 better than D2?
Vitamin D comes in two forms: D3 (cholecalciferol), usually from animal sources such as lanolin, and D2 (ergocalciferol), from plants. D3 is the form most commonly recommended and used. Vegan D3 made from lichen is available if you prefer to avoid animal-derived D3. Both raise vitamin D levels; check the label for the form and the amount.
Can you take too much vitamin D?
Yes. Taking too much over a long period can cause calcium to build up in the body, which can weaken bones and damage the kidneys and heart. The NHS advises not exceeding 100 micrograms (4,000 IU) a day for adults unless a clinician has advised a higher amount, and lower limits apply to children.
This is information, not medical advice, and is not a substitute for a registered clinician. Always read product labels and speak to your GP or pharmacist before starting a supplement, especially if you are pregnant.
Editor, Her Vitals
Oliver leads Her Vitals's editorial coverage of women's life-stage health and supplements. He curates and reviews existing branded products across trying to conceive, pregnancy, postnatal, perimenopause, menopause and the senior years, weighing what the evidence supports against guidance from bodies such as EFSA, the NHS and NICE, and is clear that the content is information rather than medical advice.
Last reviewed: 12 June 2026