Key references and resources
- NICE, Clinical Knowledge Summaries. Vitamin D deficiency in adults. January 2022.
- Vitamin D. 3 August 2020.
- Royal Osteoporosis Society. Vitamin D for bones. March 2022.
- Evidently Cochrane. Vitamin D supplements in pregnancy: what’s the latest evidence? 6 January 2022.
Key take-home points
- Vitamin D regulates calcium and phosphate homeostasis and is therefore vital for musculoskeletal health.
- The majority (80–90%) of vitamin D is synthesised in the skin in the presence of sunlight, with the remainder sourced from our diet.
- At latitudes above 40 degrees north, because of the lack of sufficient sunlight, vitamin D supplementation is vital.
- In the UK, there is insufficient ultraviolet light B from October to March for our skin to manufacture enough vitamin D.
- In the UK spring, up to 50% of the population are vitamin D insufficient and 16% are severely deficient.
- Most people with insufficient vitamin D are asymptomatic.
- Common symptoms seen in practice include muscle pain (this can mimic fibromyalgia), weakness and fatigue.
- People at high risk include older people, pregnant and lactating women, people with skin of colour, vegans, those in care homes and those on drugs such as steroids and antiepileptics.
- Routine testing of vitamin D levels is not recommended and is generally unnecessary to make the diagnosis.
- If testing vitamin D levels, know how to act on the results. If levels are >50 nmol/L, maintain through safe sun exposure and diet. If 25–50 nmol/L, treat if the patient has certain risk factors as above and maintain vitamin D through daily supplementation at a 400 international units (IU) dosage. If below 25 nmol/L, correct rapidly if symptoms of vitamin D deficiency are present and consider referral for treatment with potent antiresorptive agents. Give approximately 300,000 IU vitamin D3 orally in divided doses over 6–10 weeks. Start life-long maintenance dosing of 800 IU daily, 4 weeks after the loading dose.
- Check plasma-adjusted calcium 1 month after treating with loading doses of vitamin D.
- Whenever possible, use licensed medicine. Generic prescribing may mean an unlicensed preparation is dispensed.