Vitamin D Deficiency in the UK: Symptoms, Causes and How to Fix It

Vitamin D Deficiency in the UK: Symptoms, Causes and How to Fix It

Vitamin D deficiency is one of the most prevalent nutritional problems in the United Kingdom. Unlike most vitamins, the majority of our Vitamin D is not obtained from food — it is synthesised in the skin upon exposure to sunlight. In a country where grey skies and long winters are a fact of life, this creates a significant public health challenge.

Public Health England estimates that approximately 1 in 5 people in the UK have low Vitamin D levels [1], and the problem is particularly acute during the autumn and winter months when sunlight is insufficient for skin synthesis. In this article, we explore why Vitamin D deficiency is so common in the UK, how to recognise the symptoms, and what you can do to restore your levels.

Why Are People in the UK So Deficient in Vitamin D?

The primary source of Vitamin D for most people is ultraviolet B (UVB) radiation from sunlight, which triggers synthesis of Vitamin D3 (cholecalciferol) in the skin [2]. The problem for people living in the UK is geographical: at latitudes above approximately 51.5° North — which includes the entirety of the British Isles — the sun's angle between October and March is too low for sufficient UVB radiation to reach the skin, making it virtually impossible to synthesise meaningful amounts of Vitamin D from sunlight alone during these months [3].

Additional risk factors that increase the likelihood of deficiency include:

  • Spending most of the day indoors — office workers, the elderly, and those with limited mobility are particularly at risk
  • Darker skin tone — higher melanin content reduces UVB absorption, requiring longer sun exposure to produce equivalent Vitamin D [4]
  • Wearing covering clothing — limits skin exposure to sunlight
  • Obesity — Vitamin D is fat-soluble and can become sequestered in adipose tissue, reducing its bioavailability [5]
  • Age — the skin's capacity to synthesise Vitamin D declines significantly with age [6]
  • Certain medical conditions — including Crohn's disease, coeliac disease, and kidney or liver disorders that affect Vitamin D metabolism [7]

What Are the Symptoms of Vitamin D Deficiency?

Vitamin D deficiency can present with a wide range of symptoms, many of which are non-specific and easily attributed to other causes. Common symptoms include:

  • Fatigue and low energy — one of the most frequently reported symptoms, often dismissed as general tiredness [8]
  • Bone pain and muscle weakness — Vitamin D is essential for calcium absorption and bone mineralisation; deficiency can lead to aching bones and reduced muscle strength [9]
  • Low mood and depression — research has identified associations between low Vitamin D levels and depressive symptoms, particularly Seasonal Affective Disorder (SAD) [10]
  • Frequent illness — Vitamin D plays a key role in immune function; deficiency is associated with increased susceptibility to respiratory infections [11]
  • Hair loss — severe deficiency has been linked to alopecia areata in some studies [12]
  • Slow wound healing — Vitamin D is involved in the production of compounds that are critical for skin repair [13]

In severe or prolonged cases, Vitamin D deficiency can lead to rickets in children and osteomalacia (softening of the bones) in adults [9].

How is Vitamin D Deficiency Diagnosed?

Vitamin D status is measured via a blood test that checks the level of 25-hydroxyvitamin D (25(OH)D) in the blood. The NHS defines deficiency as a level below 25 nmol/L, with insufficiency between 25–50 nmol/L [14]. Optimal levels for health are generally considered to be above 50 nmol/L, with some researchers advocating for levels of 75 nmol/L or above for optimal immune and musculoskeletal function [15].

If you suspect you may be deficient, speak to your GP who can arrange a blood test.

What Does the NHS Recommend?

Public Health England recommends that everyone in the UK considers taking a daily Vitamin D supplement of 10 micrograms (400 IU) throughout autumn and winter [1]. Higher risk groups — including those who are rarely outdoors, have darker skin, or are over 65 — are advised to supplement year-round.

However, many nutrition researchers and clinicians argue that 400 IU is insufficient to correct an existing deficiency or achieve optimal blood levels, particularly in those who are severely deficient [15]. Doses of 1,000–4,000 IU per day are commonly used in clinical practice to restore levels, always under appropriate guidance.

Vitamin D3 vs Vitamin D2: Which Should You Take?

There are two main forms of Vitamin D used in supplements: Vitamin D2 (ergocalciferol) and Vitamin D3 (cholecalciferol). Research consistently shows that Vitamin D3 is more effective at raising and maintaining blood levels of 25(OH)D than Vitamin D2 [16]. D3 is also the form naturally produced by the skin in response to sunlight, making it the preferred choice for supplementation. Browse our full range of Vitamin D supplements to find the right strength for you.

Should You Take Vitamin D with K2?

Vitamin D3 is increasingly combined with Vitamin K2 (MK-7) in supplements, and for good reason. Vitamin D increases calcium absorption from the gut, while Vitamin K2 helps direct that calcium to the bones and teeth rather than soft tissues and arteries [17]. Taking them together may offer complementary benefits for bone health and cardiovascular protection — a topic we explore in depth in our article on Vitamin D & K2: Why You Need Both.

The Bottom Line

Vitamin D deficiency is widespread in the UK and often goes unrecognised. The combination of limited sunlight, indoor lifestyles, and dietary insufficiency means that supplementation is a practical necessity for a large proportion of the British population — particularly from October through to March.

If you are experiencing symptoms of deficiency, speak to your GP about testing. In the meantime, a high-quality Vitamin D3 supplement — ideally combined with K2 — is a simple, safe, and evidence-based step towards supporting your bone health, immune function, mood, and overall wellbeing. If you are over 50, you may also find our guide to Best Supplements for Over 50s helpful.

References

  1. Public Health England. Vitamin D and Health. PHE, 2016. Available at: https://www.gov.uk/government/publications/vitamin-d-and-health-2016
  2. Holick MF. Vitamin D deficiency. New England Journal of Medicine. 2007;357(3):266-281.
  3. Webb AR, Kline L, Holick MF. Influence of season and latitude on the cutaneous synthesis of vitamin D3. Journal of Clinical Endocrinology & Metabolism. 1988;67(2):373-378.
  4. Clemens TL, et al. Increased skin pigment reduces the capacity of skin to synthesise vitamin D3. Lancet. 1982;319(8263):74-76.
  5. Wortsman J, et al. Decreased bioavailability of vitamin D in obesity. American Journal of Clinical Nutrition. 2000;72(3):690-693.
  6. MacLaughlin J, Holick MF. Aging decreases the capacity of human skin to produce vitamin D3. Journal of Clinical Investigation. 1985;76(4):1536-1538.
  7. Bikle DD. Vitamin D metabolism, mechanism of action, and clinical applications. Chemistry & Biology. 2014;21(3):319-329.
  8. Nowson CA, Margerison C. Vitamin D intake and vitamin D status of Australians. Medical Journal of Australia. 2002;177(3):149-152.
  9. Lips P. Vitamin D deficiency and secondary hyperparathyroidism in the elderly. Endocrine Reviews. 2001;22(4):477-501.
  10. Anglin RE, et al. Vitamin D deficiency and depression in adults: systematic review and meta-analysis. British Journal of Psychiatry. 2013;202(2):100-107.
  11. Martineau AR, et al. Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data. BMJ. 2017;356:i6583.
  12. Rasheed H, et al. Serum ferritin and vitamin D in female hair loss: do they play a role? Skin Pharmacology and Physiology. 2013;26(2):101-107.
  13. Bikle DD. Vitamin D and the skin: physiology and pathophysiology. Reviews in Endocrine and Metabolic Disorders. 2012;13(1):3-19.
  14. NHS. Vitamin D. NHS.uk. Available at: https://www.nhs.uk/conditions/vitamins-and-minerals/vitamin-d/
  15. Heaney RP, et al. Human serum 25-hydroxycholecalciferol response to extended oral dosing with cholecalciferol. American Journal of Clinical Nutrition. 2003;77(1):204-210.
  16. Tripkovic L, et al. Comparison of vitamin D2 and vitamin D3 supplementation in raising serum 25-hydroxyvitamin D status: a systematic review and meta-analysis. American Journal of Clinical Nutrition. 2012;95(6):1357-1364.
  17. Vermeer C. Vitamin K: the effect on health beyond coagulation — an overview. Food & Nutrition Research. 2012;56(1):5329.
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