Medical Matters > Treatment: Vitamin D

ME Essential Spring 2022


Can Vitamin D help people with ME/CFS and are we more susceptible to Vitamin D deficiency?


Vitamin D deficiency can occur in ME/CFS and people in the moderate or severe category are at increased risk – especially if they are housebound and do not get out into the sunshine and/or are on some form of restrictive diet. So checking for vitamin D deficiency should, where appropriate, form part of the clinical assessment for ME/CFS.
Taking a daily low-dose vitamin D supplement – after taking advice from your doctor or pharmacist –  is also a sensible precautionary measure if you have ME/CFS. You can purchase a 10 microgram vitamin D3 supplement from pharmacies like Boots (other brands are available).

Treating actual vitamin D deficiency – which should always be under medical supervision – is essential. All aspects of vitamin D, and vitamin D deficiency, are covered in the ME Association information leaflet on vitamin D (see below).

Summary of key points relating to the vitamin D (25-hydroxyvitamin D) blood test:

The National Osteoporosis Society (NOS) guidelines and the Institute of Medicine (US) classify vitamin D blood test results as follows:

  • 25-hydroxyvitamin D of less than 30 nmol/L is deficient
  • 25-hydroxyvitamin D of 30-50 nmol/L may be inadequate in some people
  • 25-hydroxyvitamin D of greater than 50 nmol/L is sufficient for almost the whole population.

Low blood levels of 25-hydroxyvitamin D may mean that you are not getting enough exposure to sunlight or enough vitamin D in your food to meet your body's demand or that there is a problem with its absorption from the intestines. Occasionally, drugs used to treat seizures, particularly phenytoin (epanutin), can interfere with the liver's production of 25-hydroxyvitamin D.

High levels of 25- hydroxyvitamin D usually reflect excess supplementation from vitamin pills or other nutritional supplements.

Summary of research into vitamin D and ME/CFS:
Consider vitamin D deficiency in adults with restrictive diets and lack of access to sunlight. A retrospective study of serum 25-OH (hydroxy) vitamin D levels in 221 ME/CFS patients found moderate to severe suboptimal levels, with a mean level of 44.4nmol/l (See below). Vitamin D deficiency often goes unrecognised and can cause bone or muscle pain and muscle weakness. It can co-exist with ME/CFS. Levels < 25nmol/ml may be associated with symptoms. NB: Low serum calcium and phosphate and an elevated alkaline phosphatase are consistent with osteomalacia.

Introduction: Patients with chronic fatigue syndrome (CFS) may be at risk of osteoporosis due to their relative lack of physical activity and excessive time spent indoors, leading to reduced vitamin D synthesis. We hypothesised that serum 25-OH vitamin D levels are lower in CFS patients than in the general British population.

Subjects and Methods: We performed a retrospective survey of serum 25-OH vitamin D levels in 221 CFS patients. We compared this to a group of patients attending the hospital for other chronic conditions and to a large British longitudinal survey of 45-year old women, using a variety of appropriate statistical approaches.

Results: 25-OH vitamin D levels are moderately to severely suboptimal in CFS patients, with a mean of 44.4 nmol/L (optimal levels >75 nmol/L). These levels are lower and the difference is statistically significant (p<0.0004) than those of the general British population from a recent national survey, but similar to those in patients with other chronic conditions.

Conclusions: This data supports the recommendation made in recent NICE guidelines that all patients with moderate to severe CFS should be encouraged to obtain adequate sun exposure and eat foods high in vitamin D. Oral or intramuscular vitamin D supplementation should be considered for those whose levels remain suboptimal.

Berkovitz S et al. Serum 25-hydroxy vitamin D levels in chronic fatigue syndrome: a retrospective survey. International Journal for Vitamin and Nutrition Research | July 2009.

See also: Treatment: Vitamin D & Safety

More information

  • The ME Association has a range of detailed information written by Dr Shepherd and its dietary advisers available to download from the website shop:


Information provided by The ME Association should not be construed as medical advice. Don't assume any new or worsened symptoms are simply the result of having ME/CFS or Long Covid. We recommend that any information you deem relevant is discussed with your NHS GP as soon as possible. It is important that you seek personalised medical advice from the GP who is in charge of your care and who knows you well.

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