Vitamin D deficiency

Also called Low vitamin D, Osteomalacia, Rickets

Common in the UK because of the latitude. Everybody is advised to take a supplement in winter, and some people all year.

What it is

Vitamin D is made in the skin from sunlight and is needed to absorb calcium and keep bones and muscles working.

Between October and March the sun in the UK is too weak to make any, whatever the weather. That is a fact of latitude rather than lifestyle, which is why official advice is that everybody should consider a daily supplement of 10 micrograms through the autumn and winter.

Some people need it all year: anybody with darker skin, anybody who covers their skin, anybody who is rarely outdoors including many people in residential care, and babies and young children.

Severe deficiency causes soft bones, called rickets in children and osteomalacia in adults, with bone pain and muscle weakness. Milder deficiency is far more common, and its contribution to aches, tiredness and falls is genuinely debated rather than settled.

More is not better. Very high doses cause a dangerously raised calcium level, and high-dose supplements bought online are a real cause of harm.

Signs you might notice

Often none at all, which is why it is usually found on a blood test.

Aching bones, particularly the hips, pelvis and ribs, and tenderness when the bone is pressed.

Muscle weakness, especially getting up from a chair or climbing stairs, and a waddling walk.

Tiredness and low mood.

In children: delayed walking, bowed legs, a swollen wrist or knee, and irritability.

Recurrent falls in an older person, where muscle weakness is part of the picture.

How it can affect day-to-day life

The groups most likely to be deficient are the groups least likely to be tested: people in care homes, people with darker skin, people who do not go out, and people with a learning disability.

Supplementation is cheap and safe at recommended doses, which is why treating without testing is often reasonable and why insisting on a blood test can be a way of doing nothing.

For anybody being treated for osteoporosis, vitamin D and calcium are the foundation the other treatments are built on, and bone medication works poorly without them.

Sun exposure has to be balanced against skin cancer risk. Short periods without burning, not sunbathing, and never sunbeds.

Fortified foods, oily fish and eggs contribute, but diet alone rarely covers a UK winter.

Supporting someone well

Take 10 micrograms, which is 400 international units, daily from October to March, and all year for anybody in the higher-risk groups.

Give babies and young children the recommended supplement, including breastfed infants; formula already contains it. Healthy Start vitamins are free for those eligible.

Check care home and supported living residents are actually receiving it. This is one of the most commonly missed simple interventions in residential care.

Do not take high-dose supplements bought online without advice. Toxicity is real.

Ask for testing where there are symptoms, dark skin with no supplement, or a fracture or fall.

Pair it with calcium intake and with weight-bearing activity; the vitamin does nothing on its own.

Where to get help

A pharmacist for supplements and dosing advice; this is a good Pharmacy First question.

A GP practice for bone pain, muscle weakness, suspected rickets, or before starting treatment for osteoporosis.

Royal Osteoporosis Society have clear guidance on vitamin D, calcium and bone health.