Vitamin D deficiency is surprisingly common in the UK because sunlight is weak for much of the year and there are few natural dietary sources of the vitamin. While everyone should be aware of the importance of vitamin D, certain groups are especially vulnerable to deficiency. Identifying these at‑risk populations is critical because early intervention—through supplements, diet and lifestyle changes—can prevent long‑term health problems. This article outlines the main risk factors for vitamin D deficiency in the UK, explains why they matter and provides evidence‑based advice. For a refresher on what vitamin D does and why you need it, read our vitamin D guide.

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Why Does Vitamin D Deficiency Occur?

Your body makes most of its vitamin D when the skin is exposed to ultraviolet B (UVB) rays from sunlight. In the UK, UVB rays are strong enough for vitamin D synthesis only between April and September and around midday—and even then, cloud cover, clothing, sunscreen and darker skin can reduce production. Between October and March, there is no UVB of the appropriate wavelength, so people rely on dietary sources and supplements. Because vitamin D occurs naturally in only a few foods (oily fish, liver, egg yolks and fortified products), many people do not meet the reference nutrient intake (10 µg per day) without a supplement. Learn more about vitamin D essentials here.

Major At‑Risk Groups

People with darker skin

Melanin, the pigment that darkens the skin, reduces the ability of the skin to produce vitamin D from sunlight. The Migrant Health Guide lists people with darker skin—including those of African, African‑Caribbean and South Asian heritage—at increased risk of vitamin D deficiency. Studies show that even during summer, individuals with dark skin may not synthesise enough vitamin D, so supplementation is recommended all year round.

People who get little sun exposure

Spending most of your time indoors dramatically reduces vitamin D synthesis. This includes housebound individuals, care‑home residents, people who wear concealing clothing for cultural reasons, workers with long indoor hours, and people shielding due to illness or pandemics (e.g. COVID‑19). Find out more about symptoms and treatment of vitamin D deficiency.

Pregnant and breastfeeding women

During pregnancy and lactation, mothers supply vitamin D to their developing babies. Deficiency increases the risk of maternal bone loss and can lead to low vitamin D status in infants. The Department of Health and Social Care recommends that all pregnant women consider taking a 10 µg supplement daily. Women eligible for the Healthy Start scheme can receive free vitamin supplements containing vitamin D.

Babies and young children

Infants and toddlers grow rapidly; insufficient vitamin D impairs bone development and can cause rickets. Supplements are particularly important for children with darker skin or those who spend little time outside.

People aged over 65

Older adults produce less vitamin D in their skin and often spend more time indoors. This reduced synthesis, combined with age‑related changes in diet and kidney function, increases the risk of deficiency. Vitamin D deficiency in older adults contributes to osteomalacia, osteoporosis and increased fall risk.

People with a high body mass index (BMI)

Vitamin D is fat‑soluble and stored in fat tissue. Individuals with a high BMI have more fat stores where vitamin D can become sequestered, reducing its bioavailability. People with obesity should consider year‑round supplementation and discuss their vitamin D status with a healthcare professional. See recommended vitamin D3 vs D2 options.

People with medical conditions affecting absorption or metabolism

Certain conditions reduce the amount of vitamin D absorbed from the gut or converted into its active form. These include gastrointestinal disorders (Crohn’s disease, coeliac disease), liver disease, chronic kidney disease, and malabsorption syndromes. Such individuals may require higher doses of vitamin D and should be under medical supervision.

People taking certain medications

Some medicines accelerate vitamin D metabolism or reduce its absorption. These include anti‑convulsants, anti‑viral medicines, cholestyramine and rifampicin. People on long‑term medication should consult their doctor or pharmacist about their vitamin D needs.

People following plant‑based diets

Vegetarians and vegans often avoid animal products, which are the main natural sources of vitamin D. Although sun‑exposed mushrooms and fortified plant milks provide some vitamin D2, a daily supplement is generally necessary, particularly in autumn and winter. Lichen‑derived vitamin D3 is a vegan‑friendly option. Learn more about sources of vitamin D.

What Should At‑Risk Individuals Do?

Public health guidance in the UK recommends that adults and children over 4 years take a daily 10 µg (400 IU) supplement during the autumn and winter, and year‑round if they have little or no sunshine exposure or belong to another risk group. Babies and toddlers should receive 8.5–10 µg daily. Pregnant and breastfeeding women should also take 10 µg daily. Individuals with malabsorption or on certain medications may require higher doses and should be managed by healthcare professionals. Explore more on daily dosage guidance:

In addition to supplements, at‑risk individuals should aim to include vitamin D‑rich foods (oily fish, eggs, red meat and fortified products) and get short periods of midday sun exposure during spring and summer. Our article on vitamin D for bone health and immunity provides further insights.

Conclusion

Vitamin D deficiency is particularly common among people with darker skin, those who get little sunlight, pregnant women, young children, older adults, individuals with high BMI or malabsorption conditions, and those taking certain medications. The UK’s public health advice emphasises that these groups should take a daily supplement of 10 µg year‑round. Addressing vitamin D deficiency not only protects bone health—preventing rickets, osteomalacia and fractures—but may also support the immune system and overall wellbeing.