The requirements for producing unlicensed vitamin D are less stringent than those required of pharmaceutical grade medicines1.

Recent studies2 reveal a wide variation in the actual vitamin D content of products, particularly unlicensed formulations versus the stated dose. 

One investigation revealed 6 out of 14 unlicensed products were not within 10% of the stated dose but had a range of 8% to 201% of the dose claimed2. Another demonstrated only 5 out of 15 preparations were within 10 per cent of the stated dose2

Of these, the licensed products revealed the greatest accuracy with least variation compared with the stated dose2, as one would expect of a licenced pharmaceutical grade medicine. 

Given the fact that unlicensed products are uncontrolled, this means that they are not guaranteed to contain the correct dose of vitamin D. As well as being more expensive, these products also have the potential to expose patients to risk.  Subsequently, the best way forward is to use licensed vitamin D3 products authorised by the UK Medicines Healthcare Products Regulatory Authority (MHRA) for efficacy, safety and quality.3 Typically, these are available by prescription, rather than supermarket or OTC purchase

We acknowledge that excerpts from an article written by Dr Emma Derbyshire, published in the dietetics journal, Clinical Nutrition have been used (with permission) in the website.  The article is entitled Vitamin D Deficiency - Health conditions, signs and supplement considerations. CN; 16(2): 47-49


  1. Good Manufacturing Practice and Good Distribution Practice.  Available at
  2. Eligar V, Davies JS (2014) Vitamin D prescribing: the issues with unlicensed products. Prescriber December; 7-8.