Vitamin D deficiency is a common yet often overlooked condition affecting millions across the UK, particularly during autumn and winter months when sunlight exposure is limited. Recognising low vitamin D signs early is crucial, as deficiency can lead to significant musculoskeletal problems, increased fall risk, and impaired bone health. Symptoms are frequently non-specific—ranging from bone pain and muscle weakness to persistent fatigue—making clinical recognition challenging without blood testing. Certain groups, including older adults, individuals with darker skin, and those with limited sun exposure, face substantially elevated risk. This article explores the key signs of vitamin D deficiency, who is most vulnerable, and how diagnosis and treatment are managed within the NHS framework.

Common Signs and Symptoms of Low Vitamin D

Vitamin D deficiency often develops insidiously, and many individuals remain asymptomatic until levels become severely depleted. When symptoms do manifest, they tend to be non-specific, which can make clinical recognition challenging without biochemical confirmation.

Musculoskeletal symptoms are amongst the most frequently reported manifestations. Patients may experience diffuse bone pain, particularly affecting the ribs, hips, pelvis, and lower limbs. Muscle weakness, especially in proximal muscle groups, can lead to difficulty climbing stairs, rising from a seated position, or maintaining balance. This myopathy may increase fall risk, particularly in older adults. Some individuals report a generalised sense of fatigue and low energy that persists despite adequate rest.

Mood changes have been associated with low vitamin D status, though the relationship remains complex and evidence is inconsistent. Some patients report low mood, increased anxiety, or seasonal affective symptoms, particularly during winter months when sunlight exposure is limited. However, there is no established causal link between vitamin D deficiency and clinical depression, and these associations require further research.

In children, severe deficiency can lead to rickets, characterised by delayed growth, bone deformities (such as bowed legs), dental problems, and skeletal pain. Adults with prolonged deficiency may develop osteomalacia, presenting with bone tenderness, fractures with minimal trauma, and a waddling gait. It is important to note that many people with suboptimal vitamin D levels experience no obvious symptoms.

Seek urgent medical attention if you or your child experiences severe bone pain, new fractures with minimal trauma, progressive bone deformities, or symptoms of low calcium such as muscle cramps, tingling, or seizures. For persistent bone pain, unexplained muscle weakness, or recurrent falls, contact your GP for assessment.

Who Is at Risk of Vitamin D Deficiency?

Certain population groups face substantially elevated risk of vitamin D deficiency due to reduced cutaneous synthesis, inadequate dietary intake, or increased physiological requirements. Understanding these risk factors enables targeted screening and preventative strategies.

Individuals with limited sun exposure constitute a major at-risk group. This includes people who are housebound, institutionalised, or who cover their skin for cultural or religious reasons. Those working predominantly indoors or living in northern latitudes (including much of the UK) receive insufficient ultraviolet B (UVB) radiation, particularly between October and March when the sun's angle prevents adequate vitamin D synthesis.

Skin pigmentation significantly affects vitamin D production. People with darker skin tones have higher melanin concentrations, which reduces UVB penetration and decreases cutaneous vitamin D synthesis. South Asian, African, Caribbean, and Middle Eastern populations living in the UK are therefore at increased risk and should consider year-round supplementation, as advised by Public Health England.

Older adults (aged 65 years and above) experience reduced dermal synthesis capacity and often have decreased outdoor activity. Pregnant and breastfeeding women have increased vitamin D requirements to support foetal skeletal development and maintain their own bone health. Exclusively breastfed infants are at risk unless receiving supplementation, as breast milk contains limited vitamin D.

Obesity (BMI ≥30 kg/m²) is associated with lower bioavailable vitamin D due to sequestration in adipose tissue. Individuals with malabsorption disorders such as coeliac disease, Crohn's disease, or those who have undergone bariatric surgery may have impaired vitamin D absorption. Chronic kidney disease and liver disease can affect vitamin D metabolism and activation.

Certain medications increase deficiency risk, including some anticonvulsants, glucocorticoids, rifampicin, and some antiretrovirals, as they can accelerate vitamin D metabolism. NICE recommends that healthcare professionals maintain heightened awareness of these risk factors when assessing patients.

How Low Vitamin D Is Diagnosed in the UK

Diagnosis of vitamin D deficiency in the UK relies primarily on serum 25-hydroxyvitamin D [25(OH)D] measurement, which reflects both dietary intake and cutaneous synthesis. This is the most stable and abundant circulating form of vitamin D, making it the preferred biomarker for assessing vitamin D status.

Interpretation of serum levels follows UK guidance from NICE and the Scientific Advisory Committee on Nutrition (SACN). Generally, serum 25(OH)D concentrations below 25 nmol/L indicate deficiency, levels between 25–50 nmol/L suggest insufficiency, and concentrations above 50 nmol/L are considered sufficient for most individuals. These thresholds are used to guide clinical management in the UK.

NHS guidance emphasises that routine screening is not recommended for the general population. Testing should be reserved for individuals presenting with symptoms suggestive of deficiency (such as bone pain or proximal myopathy) or those with identified risk factors. This targeted approach helps ensure appropriate resource utilisation whilst identifying those most likely to benefit from intervention.

Additional investigations may be warranted when deficiency is confirmed or suspected. Serum calcium, phosphate, alkaline phosphatase, and parathyroid hormone (PTH) levels can help assess the functional impact of deficiency and exclude secondary hyperparathyroidism. Baseline calcium should be checked before initiating high-dose vitamin D therapy. In cases of suspected osteoporosis, bone density scanning (DEXA) may be indicated to evaluate fracture risk. X-rays might be considered if osteomalacia is suspected, potentially showing characteristic features such as Looser's zones.

Blood samples can be taken at any time of day, and fasting is not required. Results are typically available within one to two weeks through NHS laboratories. If you believe you may be at risk of vitamin D deficiency, discuss testing with your GP, who can determine whether investigation is clinically appropriate based on your individual circumstances and risk profile.

Treatment Options for Vitamin D Deficiency

Management of vitamin D deficiency involves supplementation to restore adequate serum levels, followed by maintenance therapy to prevent recurrence. Treatment regimens vary according to deficiency severity, patient age, and underlying risk factors.

Loading (treatment) doses are used for confirmed deficiency. Adults typically receive colecalciferol (vitamin D3), which is generally preferred over ergocalciferol (vitamin D2) due to superior bioavailability. UK guidance recommends a total loading dose of approximately 300,000 IU over 6-10 weeks. Common regimens include colecalciferol 50,000 IU weekly for 6 weeks, 20,000 IU twice weekly for 7 weeks, or 4,000 IU daily for 10 weeks. The specific regimen should be individualised based on baseline serum levels and clinical context.

Following the loading phase, maintenance therapy is essential to sustain adequate vitamin D status. For those who have been treated for deficiency, maintenance doses typically range from 800-2,000 IU (20-50 micrograms) daily. This is higher than the general population recommendation of 400 IU (10 micrograms) daily during autumn and winter. Maintenance therapy is typically continued long-term, particularly when modifiable risk factors persist.

Monitoring response to treatment involves checking serum calcium about one month after completing the loading course, with repeat serum 25(OH)D measurement at around three months if clinically indicated. This confirms adequate repletion and guides ongoing management.

Vitamin D preparations are available over-the-counter and on prescription. Local NHS prescribing policies may restrict routine vitamin D prescribing in line with self-care guidance. Combination products containing calcium and vitamin D are available for individuals with concurrent calcium insufficiency or osteoporosis.

Cautions include hypercalcaemia, severe kidney disease, granulomatous disorders (such as sarcoidosis), and history of kidney stones. Vitamin D may interact with certain medications, including thiazide diuretics and digoxin. The safe upper limit for adults is 4,000 IU (100 micrograms) daily. Report suspected side effects from vitamin D medicines to the MHRA Yellow Card scheme (yellowcard.mhra.gov.uk).

Preventing Low Vitamin D Levels

Prevention of vitamin D deficiency requires a multifaceted approach combining sensible sun exposure, dietary optimisation, and targeted supplementation for at-risk groups. Public Health England provides clear guidance to support population-level vitamin D sufficiency.

Sunlight exposure remains the primary natural source of vitamin D for most people. During spring and summer months (late March to September), short periods of regular sun exposure on bare forearms, hands, or lower legs can support vitamin D synthesis. The exact time needed varies by skin type, time of day, and weather conditions—the NHS advises short, regular exposure without burning. Those with darker skin may require longer exposure times. However, it is important to balance vitamin D production with skin cancer prevention; prolonged unprotected sun exposure should be avoided, and sunscreen should be applied when spending extended periods outdoors.

Dietary sources contribute to vitamin D status, though few foods naturally contain significant amounts. Oily fish (such as salmon, mackerel, sardines, and trout) are excellent sources, providing 400–1,000 IU per serving. Other sources include egg yolks (approximately 40 IU per egg), red meat, and liver. In the UK, some foods are fortified with vitamin D, including some fat spreads, breakfast cereals, plant-based drinks, and infant formula milk. However, dietary intake alone is typically insufficient to maintain optimal levels, particularly during winter months.

Supplementation recommendations from Public Health England advise that everyone should consider taking a daily supplement containing 10 micrograms (400 IU) of vitamin D during autumn and winter. Certain groups should take supplements year-round, including individuals with limited sun exposure, those with darker skin, older adults, and pregnant or breastfeeding women. Children aged one to four years should receive a daily supplement of 10 micrograms, whilst infants under one year require 8.5–10 micrograms daily unless consuming 500ml or more of infant formula.

Healthy Start vitamins, which include vitamin D, are available free to eligible pregnant women and families with young children. Maintaining awareness of your risk factors and following national guidance can significantly reduce your likelihood of developing vitamin D deficiency. If you are uncertain whether supplementation is appropriate for you, consult your GP or pharmacist for personalised advice.

Frequently Asked Questions