Vitamin D deficiency: prevention and management in primary care

In this CPD eLearning module, GP Dr Roger Henderson provides an overview of vitamin D metabolism, deficiency and the key preventive and management strategies undertaken in primary care.

Complete the full module on Nursing in Practice 365 today

Module summary

Vitamin D deficiency is a widespread and often under-recognised public health concern. It is estimated that around one in six adults in the UK have low vitamin D levels, particularly during winter and spring months when ultraviolet B (UVB) exposure is limited.

Inadequate vitamin D leads to disturbed calcium and phosphate metabolism, resulting in bone and muscle disorders such as osteomalacia in adults and rickets in children. Some emerging evidence has also linked deficiency to falls, frailty and possibly immune dysregulation, cardiovascular disease and depression.

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Nurses working in primary care are ideally placed to identify at-risk individuals, promote preventive measures through education and lifestyle advice and provide evidence-based vitamin D supplementation.

This module provides an up-to-date overview of vitamin D functions, deficiency states, clinical assessment and management in adults and children, with emphasis on current UK guidance and prescribing recommendations.

Learning objectives

By the end of this module, you should be able to:

Explain the key physiological roles of vitamin D.
Describe the prevalence and risk factors associated with deficiency in the UK.
Recognise the clinical features of mild and severe deficiency.
Identify appropriate indications for vitamin D testing and interpret results accurately.
Apply national guidance on supplementation, lifestyle and dietary advice.
Understand when vitamin D can be prescribed on the NHS and when over-the-counter supplementation is appropriate.
Promote patient self-care and population-level prevention strategies.

Overview of vitamin D

Vitamin D is a fat-soluble steroid hormone, essential for calcium and phosphate balance and bone mineralisation. Two main forms are important for health:

Vitamin D₂ (ergocalciferol) – derived from plant sources and fungi, and used in some supplements.
Vitamin D₃ (cholecalciferol) – synthesised in skin exposed to ultraviolet light B, and also found in animal products such as oily fish and eggs.

Dietary sources alone rarely provide sufficient vitamin D and approximately 80% to 90% of the body’s requirement is normally obtained through sunlight exposure. This dependency explains the pronounced seasonal variation in vitamin D status seen in the UK and northern Europe.

Vitamin D metabolism and functions

After formation in the skin or ingestion from diet, vitamin D undergoes two hydroxylation steps:

In the liver it is converted to 25-hydroxyvitamin D [25(OH)D] – the major circulating form and the best indicator of status.
In the kidneys it is further hydroxylated to 1,25-dihydroxyvitamin D [1,25(OH)₂D] – the biologically active hormone (calcitriol).

Calcitriol binds to vitamin D receptors in the gut, bone, muscle and immune cells, regulating:

Intestinal calcium and phosphate absorption.
Bone mineralisation and prevention of rickets/osteomalacia.
Muscle strength and balance, helping in reducing falls in older adults.
Modulation of immune and cell-growth pathways.
Deficiency can also result in secondary hyperparathyroidism, leading to bone resorption, muscle weakness and skeletal deformities in children.

Epidemiology and risk factors

Vitamin D deficiency is common globally and across all age and ethnic groups. UK data from the National Diet and Nutrition Survey showed that approximately 20% of adults and 16% of children have 25(OH)D levels below 25nmol/L during winter and spring.

Higher prevalence occurs among:

Individuals with limited sun exposure (such as the housebound, institutionalised, or those covering their skin for cultural or medical reasons).
People with darker skin tones such as those of African, African-Caribbean and South-Asian heritage.
Older adults, who have reduced dermal synthesis and renal hydroxylation capacity.
Obese individuals, since vitamin D is sequestered in adipose tissue.
People with malabsorption (such as in coeliac disease, inflammatory bowel disease, and pancreatic insufficiency) or those with chronic liver or kidney disease.⁵
Socioeconomic deprivation, indoor occupations and northern latitude also contribute to a higher risk.

Clinical presentation

Mild deficiency/ insufficiency

People who are mildly deficient in vitamin D are often asymptomatic and detected incidentally when being medically investigated for other reasons. Patients may report these symptoms:

General non-specific fatigue.
Low mood.
Muscle aches (particularly proximal myopathy).
Bone or joint pain, especially in the hips, legs or back.

Severe deficiency

Diffuse bone pain and tenderness.
Muscle weakness, such as difficulty rising from a chair or being able to climb stairs.
A waddling gait or stooped posture.
Fragility fractures or falls in older adults.
In children: skeletal deformities (bowed legs, widened wrists), delayed motor milestones, hypocalcaemic seizures.
Because symptoms are non-specific, a high level of clinical suspicion is essential, particularly in the at-risk groups.

Complete the full module on Nursing in Practice 365 and log 1.5 CPD hours for your appraisal

Dr Roger Henderson is a GP in Scotland