Vitamin D deficiency symptoms can be subtle and often develop gradually, making the condition difficult to recognise without blood testing. In the UK, vitamin D deficiency is particularly common due to limited sunlight exposure, especially during autumn and winter months when ultraviolet B radiation is insufficient for the body to produce adequate amounts. Symptoms typically include bone pain, muscle weakness, persistent fatigue, and difficulty with mobility. Severe deficiency can lead to rickets in children and osteomalacia in adults. Understanding the signs of vitamin D deficiency is essential for early detection and appropriate treatment, particularly for high-risk groups including older adults, people with darker skin tones, and those with limited sun exposure.

What Is Vitamin D Deficiency?

Vitamin D deficiency occurs when the body does not have sufficient levels of vitamin D to maintain optimal health. In the UK, serum 25-hydroxyvitamin D (25(OH)D) concentrations below 25 nmol/L are generally considered deficient, whilst levels between 25–50 nmol/L indicate insufficiency. Levels above 50 nmol/L are generally adequate for bone health, though optimal levels for non-skeletal outcomes remain uncertain. Vitamin D is a fat-soluble vitamin that plays a crucial role in calcium and phosphate metabolism, bone health, immune function, and cellular processes throughout the body.

The body produces vitamin D primarily through skin exposure to ultraviolet B (UVB) radiation from sunlight. A smaller proportion comes from dietary sources such as oily fish, egg yolks, and fortified foods. Once synthesised or ingested, vitamin D undergoes hydroxylation in the liver to form 25(OH)D, then further conversion in the kidneys to the active hormone calcitriol (1,25-dihydroxyvitamin D).

Vitamin D deficiency is particularly common in the UK due to limited sunlight exposure, especially during autumn and winter months when UVB radiation is insufficient for cutaneous synthesis. The condition can affect people of all ages, from infants to older adults, and may develop gradually over months or years. Severe deficiency can lead to metabolic bone diseases such as rickets in children and osteomalacia in adults, whilst milder deficiency may contribute to reduced bone density and increased fracture risk.

The UK Government recommends that everyone should consider taking a daily supplement containing 10 micrograms (400 IU) of vitamin D, particularly during the autumn and winter months, to maintain adequate levels and support musculoskeletal health. Routine testing for vitamin D is not recommended for the general population but may be appropriate for those with symptoms or in high-risk groups.

Common Symptoms of Vitamin D Deficiency

The symptoms of vitamin D deficiency can be subtle and non-specific, often developing insidiously over time. Many individuals with mild to moderate deficiency may be asymptomatic, with the condition only detected through blood testing. However, as deficiency becomes more pronounced, various clinical manifestations may emerge.

Musculoskeletal symptoms are amongst the most characteristic features:

• Bone pain and tenderness, particularly in the ribs, hips, pelvis, and lower limbs

• Muscle weakness, especially affecting proximal muscle groups (thighs and upper arms)

• Muscle aches and generalised myalgia

• Difficulty climbing stairs or rising from a seated position

• Increased susceptibility to falls, particularly in older adults

General symptoms may include:

• Persistent fatigue and low energy levels

• Some studies suggest associations with mood changes, though evidence is mixed and not diagnostic

• There is limited evidence regarding links with immune function, infections, and wound healing

In children, severe deficiency can cause rickets, characterised by delayed growth, skeletal deformities (bowed legs, knock knees), delayed tooth eruption, and craniotabes (soft skull bones). Adults with prolonged severe deficiency may develop osteomalacia, presenting with bone pain, muscle weakness, and an increased risk of fractures, particularly in the hip, spine, and wrist.

It is important to note that these symptoms are non-specific and can occur in numerous other conditions. If you experience persistent musculoskeletal symptoms, unexplained fatigue, or have risk factors for vitamin D deficiency, consult your GP for appropriate assessment. Initial investigations may include serum 25(OH)D, adjusted calcium, phosphate, alkaline phosphatase (ALP), parathyroid hormone (PTH), and kidney function tests.

Seek urgent medical attention if a child shows signs of rickets (bone deformities, delayed development), or if you experience severe bone pain, unexplained fractures, or symptoms of hypocalcaemia (muscle spasms, tingling around the mouth or in fingers).

Who Is at Risk of Vitamin D Deficiency?

Certain population groups in the UK face a substantially higher risk of developing vitamin D deficiency due to physiological, environmental, or lifestyle factors. Understanding these risk factors is essential for targeted prevention and early intervention.

High-risk groups include:

• People with darker skin tones (African, African-Caribbean, and South Asian backgrounds) require longer sun exposure to synthesise equivalent amounts of vitamin D due to higher melanin content, which reduces UVB penetration

• Individuals with limited sun exposure, including those who are housebound, institutionalised, living in care homes, or who cover their skin for cultural or religious reasons

• Older adults (aged 65 years and above), as skin synthesis capacity declines with age and mobility limitations may reduce outdoor activity

• Infants and young children, particularly those who are exclusively breastfed (who should receive vitamin D supplementation from birth)

• Pregnant and breastfeeding women, who have increased vitamin D requirements

Medical conditions that increase deficiency risk include:

• Malabsorption disorders (coeliac disease, Crohn's disease, ulcerative colitis, cystic fibrosis)

• Chronic kidney disease, which impairs conversion to active vitamin D

• Liver disease affecting hydroxylation processes

• Obesity, as vitamin D is sequestered in adipose tissue

Medications that may affect vitamin D metabolism include:

• Enzyme-inducing antiepileptics (carbamazepine, phenytoin, primidone)

• Glucocorticoids

• Rifampicin

• Antiretrovirals

• Orlistat

• Cholestyramine

Lifestyle factors such as spending most time indoors, working night shifts, or living in northern latitudes (the entire UK experiences insufficient UVB radiation from October to March) further compound risk. The NHS recommends that individuals in high-risk groups should take daily vitamin D supplements throughout the year, not just during winter months. If you belong to one or more risk categories, discuss supplementation and potential testing with your GP or practice nurse.

Treatment Options for Vitamin D Deficiency

Treatment of vitamin D deficiency in the UK follows guidance from NICE and professional bodies, with the approach tailored to the severity of deficiency and individual patient factors. The primary treatment modality is vitamin D supplementation, available in various formulations and dosing regimens.

For confirmed deficiency (serum 25(OH)D below 25 nmol/L), treatment typically involves:

• Loading therapy with high-dose colecalciferol (vitamin D3), commonly prescribed as a total of approximately 300,000 IU over 6-10 weeks, such as:
• 50,000 IU once weekly for 6 weeks, or
• 20,000 IU twice weekly for 7 weeks, or

• Alternative daily regimens (e.g., 4,000-5,000 IU daily for 8-10 weeks)

• Maintenance therapy following loading, usually 800–2,000 IU (20–50 micrograms) daily, or equivalent weekly doses

Colecalciferol (vitamin D3) is generally preferred over ergocalciferol (vitamin D2) due to superior bioavailability and sustained serum levels. Intramuscular vitamin D preparations are not routinely recommended in UK primary care and should only be considered under specialist advice, as they are often unlicensed for this indication.

Calcium co-supplementation may be necessary in certain situations, particularly in older adults at risk of osteoporosis or those with dietary calcium insufficiency. However, calcium should not be routinely added without assessment, as excessive intake carries cardiovascular considerations.

Monitoring and safety:

• Check adjusted calcium levels at baseline and 1 month after loading therapy

• Reassessment of serum 25(OH)D levels after 3–4 months of treatment

• Do not exceed 4,000 IU (100 micrograms) daily without clinical supervision

• Use with caution in sarcoidosis, other granulomatous disorders, primary hyperparathyroidism, or history of renal stones

• Consider potential interactions with thiazide diuretics, digoxin, orlistat, and cholestyramine

Vitamin D supplements for prevention are available over-the-counter and, in line with NHS England self-care guidance, should not routinely be prescribed. Prescription treatment is appropriate for confirmed deficiency or specific clinical indications. Certain groups, including pregnant women, children under four, and those on specific benefits, may be eligible for free Healthy Start vitamins. Report suspected side effects of vitamin D medicines via the MHRA Yellow Card scheme. If you experience symptoms such as nausea, excessive thirst, confusion, or abdominal pain whilst taking supplements, contact your GP promptly.

Preventing Vitamin D Deficiency in the UK

Prevention of vitamin D deficiency in the UK requires a multifaceted approach combining sensible sun exposure, dietary optimisation, and targeted supplementation, particularly given the country's northern latitude and climate.

Sunlight exposure remains the most natural source of vitamin D. During late March to September:

• Spend short, regular periods in the sun with forearms, hands or lower legs uncovered

• Take care not to burn – sun protection is still important

• You can make vitamin D while using sunscreen, though it may reduce the amount produced

• The time needed varies by skin type, time of day, and weather conditions

However, from October through early March, UVB radiation at UK latitudes is insufficient for cutaneous vitamin D production, making alternative sources crucial during these months.

Dietary sources can contribute to vitamin D status, though few foods naturally contain significant amounts:

• Oily fish (salmon, mackerel, sardines, herring) — richest natural sources

• Egg yolks, red meat, and liver — modest amounts

• Fortified foods including some breakfast cereals, fat spreads, and dairy alternatives (check labels as fortification levels vary)

Despite dietary efforts, it is challenging to obtain sufficient vitamin D from food alone, particularly during winter.

Supplementation strategy as recommended by UK Government guidance:

• Everyone should consider taking 10 micrograms (400 IU) daily during autumn and winter

• High-risk groups should take daily supplements year-round

• Infants from birth to one year should receive 8.5–10 micrograms daily (unless consuming 500ml or more of infant formula daily, which is fortified)

• Children aged 1–4 years should receive 10 micrograms daily

• Adults should not exceed 100 micrograms (4,000 IU) daily without medical supervision

Pregnant and breastfeeding women should ensure adequate intake through supplementation, as maternal vitamin D status affects foetal skeletal development and infant stores. The NHS Healthy Start scheme provides free vitamins to eligible families. Regular physical activity, maintaining a healthy weight, and managing chronic conditions that affect vitamin D metabolism also support optimal status. Discuss your individual requirements with your GP or a registered dietitian, particularly if you have medical conditions or take medications that may interact with vitamin D supplementation.

Frequently Asked Questions