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Ep 68 – Vitamin D deficiency in adults


Posted 17 Mar 2023

Dr Roger Henderson

Vitamin D is a fat-soluble vitamin that is essential for human health. It regulates calcium and phosphate homeostasis and is therefore vital for musculoskeletal functioning. In the UK, up to 50% of the adult population may be vitamin D insufficient following the winter months, with one in six being severely deficient. In this podcast, Dr Roger Henderson looks at who is most at risk of vitamin D deficiency, how it should be diagnosed, what treatment options are available and why unlicensed vitamin D preparations should not be recommended.


Key references and resources

  1. NICE, Clinical Knowledge Summaries. Vitamin D deficiency in adults. January 2022.
  2. Vitamin D. 3 August 2020.
  3. Royal Osteoporosis Society. Vitamin D for bones. March 2022.
  4. 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.

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