In short: Vitamin D helps the body absorb calcium and phosphate to keep bones, teeth and muscles healthy. In the UK, sunlight is too weak to make vitamin D from about October to early March, so the NHS advises everyone to consider a daily 10 microgram (400 IU) supplement in autumn and winter, and certain higher-risk groups to take it all year. Low levels often cause no symptoms at first, but long-term deficiency can lead to bone pain and muscle weakness.

This guide, written by a Ready Health prescribing pharmacist, explains who is at risk, what symptoms to look out for and how much vitamin D UK guidance recommends.

What is vitamin D and why do we need it?

Vitamin D is made in the skin when it is exposed to direct sunlight, and smaller amounts come from food. Its main job is to help regulate calcium and phosphate, which are needed for healthy bones, teeth and muscles. In children, severe deficiency can cause rickets; in adults, it can cause osteomalacia (softening of the bones).

What are the symptoms of vitamin D deficiency?

Many people with low vitamin D have no obvious symptoms. When symptoms do occur, they can include:

Bone pain or aching, particularly in the lower back, hips, legs or ribs
Muscle weakness, aches or cramps
Difficulty climbing stairs or getting up from a low chair
In children, delayed growth, bowed legs or bone deformities

Tiredness and low mood are often linked to vitamin D online, but these symptoms have many possible causes and the evidence that vitamin D supplements improve them is limited. If you feel persistently tired or low, it is worth getting checked for other causes too.

Who is most at risk of low vitamin D?

The NHS advises a daily 10 microgram supplement throughout the year for people who:

Are rarely outdoors, for example if frail or housebound
Live in a care home
Usually cover most of their skin when outdoors
Have dark skin, for example people of African, African-Caribbean or South Asian background

Other factors that can increase risk include obesity, certain bowel conditions that affect absorption (such as coeliac or Crohn's disease), kidney or liver disease, some medicines (such as certain anti-epileptic medicines), and pregnancy or breastfeeding.

How much vitamin D should you take?

UK recommendations are based on advice from the Scientific Advisory Committee on Nutrition (SACN).

Group	Recommended daily supplement	Do not exceed (daily)
Adults and children aged 11 and over (including pregnancy and breastfeeding)	10 micrograms (400 IU): autumn and winter, or all year if at higher risk	100 micrograms (4,000 IU)
Children aged 1 to 4	10 micrograms all year	50 micrograms (2,000 IU) for ages 1 to 10
Babies under 1 (breastfed, or having less than 500ml formula a day)	8.5 to 10 micrograms all year	25 micrograms (1,000 IU)

Formula is already fortified, so babies having 500ml or more a day do not usually need an extra supplement. If a clinician has diagnosed deficiency, they may recommend a different, short-term treatment dose. Follow their advice rather than the general amounts above, and do not take high-dose products without medical advice, because too much vitamin D over a long period can raise calcium levels and harm the kidneys and heart.

How can you get more vitamin D naturally?

Sunlight: from late March or early April to the end of September, most people make enough from short periods outdoors. Cover up or use sunscreen before your skin starts to turn red or burn.
Food: oily fish (salmon, mackerel, sardines, herring), egg yolks, red meat and fortified foods such as some breakfast cereals and fat spreads. Food alone rarely provides enough.

Should you have a vitamin D blood test?

Routine testing is not needed for most people, who can simply follow the supplement advice above. A test may be useful if you have symptoms suggesting deficiency, a condition affecting bones or absorption, or several risk factors. Results are usually reported in nmol/L. As a general guide used in UK practice, levels below 25 nmol/L indicate deficiency, 25 to 50 nmol/L may be inadequate for some people, and above 50 nmol/L is considered sufficient for most. A clinician will interpret your result alongside your symptoms and history.

Frequently asked questions

Can I get enough vitamin D from sunlight in winter in the UK?

No. Between October and early March, UK sunlight does not contain enough UVB for your skin to make vitamin D, which is why supplements are advised.

Is it safe to take vitamin D every day?

Yes, 10 micrograms a day is a safe amount for adults and children over 1. Avoid exceeding the upper limits unless a clinician has advised it.

Can you take too much vitamin D?

Yes, from supplements (not from sunlight). Long-term excess can lead to high calcium levels in the blood.

Does vitamin D help with tiredness?

If tiredness is due to proven deficiency, treating it may help. For most people, tiredness has other causes, so it is worth getting it properly assessed.

Key takeaways

The NHS advises everyone in the UK to consider 10 micrograms of vitamin D a day in autumn and winter.
Higher-risk groups, including people with dark skin and those rarely outdoors, should take it all year.
Deficiency is often symptomless but can cause bone pain and muscle weakness.
Do not exceed 100 micrograms a day as an adult unless advised by a clinician.

Sources and further reading

Last reviewed: October 2026 by Shamir Patel, Independent Prescribing Pharmacist, Ready Health. This article is general information and does not replace advice from your own clinician.

If you would like your levels checked, read about our vitamin D blood test in Wigan or see our private blood tests at Ready Health in Standish.