CPD: Challenges in vitamin D deficiency

In this CPD module, endocrinologists Dr Zahra Ravat and Dr Zaki Hassan-Smith discuss key challenges in identifying and managing vitamin D deficiency in primary care, including interpretation of tests, when investigations are required, recommended treatment to correct levels and long-term management.

Complete the full module on Pulse 365 today.

Learning objectives

This module will support your knowledge of how to manage challenges in vitamin D deficiency, including:

• Identifying which patients should be assessed for vitamin D deficiency and when testing is appropriate.
• Interpreting serum vitamin D levels and recognising deficiency, insufficiency, and sufficiency thresholds.
• Recommending appropriate vitamin D supplementation, including first-line treatment, dosing regimens, and maintenance dosages.
• Recognising when additional investigations or specialist referral are needed, especially in complex or refractory cases.
• Monitoring and follow-up, including checking serum calcium levels and repeat testing.

1. Which patients should have their Vitamin D levels measured?

Guidelines and consensus opinion statements in this area have had to balance the benefit from having knowledge of vitamin D status against the large health economic costs associated with widespread testing. Therefore focus has been on patients with symptoms of severe vitamin D deficiency or osteomalacia, where vitamin D testing is helpful for diagnosis purposes, or in patients with suspected metabolic bone diseases, such as osteoporosis, where this information will guide management, or in those with known disease prior to starting treatment with anti-resorptive agent.^1,2 Vitamin D supplementation has beneficial effects on musculoskeletal health in osteoporosis and osteomalacia.^3,4

There is a wide spectrum of vitamin D insufficiency and deficiency. In severe cases, nutritional rickets can occur in children and is associated with defective chondrocyte development and bone mineralisation. There has been a resurgence in this condition, and the consequences can be severe and include characteristic lower limb deformities, bone pain, failure to thrive, developmental delay and even cardiomyopathy, tetany and seizures. Public health advice, testing and supplementation strategies have been implemented with an aim to prevent this condition. In adults, osteomalacia can be associated with bone and muscle pain, weakness, a characteristic waddling gait, muscle cramps and symptoms of hypocalcaemia. These conditions may be diagnosed after recognition of symptoms and a characteristic biochemical pattern, including low or normal serum adjusted calcium, low serum phosphate, and increased markers of bone turnover such as alkaline phosphatase or parathyroid hormone. Assessment of vitamin D status would be made to confirm the diagnosis. In routine clinical practice this would usually be by testing total vitamin D (25(OH)D). At the less severe end of the spectrum, vitamin D deficiency can present with non-specific symptoms, including widespread aches and pains and fatigue.

Vitamin D status should be assessed in secondary care in patients with suspected or known metabolic bone diseases, or where osteomalacia/rickets and secondary hyperparathyroidism are suspected.^1,5,6 In the context of osteoporosis and Paget’s disease  vitamin D status should be assessed, along with U+Es and bone profiles prior to the use of potent anti-resorptive medications such as zoledronate and denosumab to prevent severe hypocalcaemia post-treatment, which can result in hospital admission and prolonged treatment with calcium and vitamin D.¹  In patients with suspected primary hyperparathyroidism, vitamin D status can be helpful in interpretation of tests results prior to diagnosis, particularly where adjusted calcium concentrations are only mildly elevated. Advice from metabolic bone specialists may be helpful in such circumstances.

The Royal Osteoporosis Society advise that vitamin D levels should not be routinely assessed in asymptomatic individuals at low risk of deficiency.⁵ This is supported by a recent systematic review which found that there was little proven overall health benefit to endorse routine vitamin D screening of asymptomatic populations, given theoretical patient harms and economic burden.^7,8 Consensus opinion advises supplementation rather than checks of vitamin D in asymptomatic patients who are at increased risk of vitamin D deficiency (such as those with obesity, low sun exposure, darker skin and the elderly), as testing for deficiency would not change the management approach.¹ There is also useful information available from the Royal Osteoporosis Society, and NICE Clinical Knowledge Summaries.

How should the results be interpreted and how should deficiency/insufficiency states be treated?

In routine practice in the UK, the following serum vitamin D thresholds are in use:

• Vitamin D deficiency (may be associated with an increased risk of adverse outcomes): <25 nmol/L.
• Vitamin D insufficiency (concentrations may be inadequate for some people): 25-50 nmol/L.
• Sufficient Vitamin D status (sufficient for most people): >50 nmol/L.

These thresholds have been supported by various bodies such as the Institute of Medicine (IOM), the Scientific Advisory Committee on Nutrition (SACN) and the Royal Osteoporosis Society (ROS), and are largely based on preventing adverse bone related outcomes and severe presentations associated with osteomalacia and rickets.^1,9 It is debated whether these levels apply to the full range of non-skeletal outcomes.

Practical lifestyle advice should be offered to all patients irrespective of vitamin D status, this includes the importance of natural sunlight exposure and calcium-rich diets in maintaining vitamin D levels.^1,6 In general, patients with vitamin D deficiency should be treated by supplementation, along with those with insufficiency, particularly where there is presence of risk factors such as osteoporosis or increased risk of fracture, those taking anti-resorptive medications and in those at risk of vitamin D deficiency. The IOM’s report on integrated bone health outcomes found a serum 25(OH)D concentration of 40nmol/L would meet requirements in 50% of the population.^9,10 The ROS advises treatment in insufficiency states in patients at risk of fractures (such as high fracture risk, previous fragility fractures, confirmed osteoporosis, glucocorticoid users); in patients at risk of developing vitamin D deficiency in the near future (such as those at high risk or symptomatic of deficiency, those with malabsorption and those taking medications which interfere with vitamin D metabolism, eg, anti-epileptics, anti-fungal and steroids medications), and that at risk of complications (such as those with raised parathyroid hormone, those initiating or taking anti-resorptive medications).^1,2 

First-line treatment of vitamin D insufficiency or deficiency is with oral preparations of vitamin D3 (colecalciferol). Vitamin D2 (ergocalciferol) is an alternative option for those unable to take vitamin D3 for dietary reasons.^1,3,12  Maintenance treatment doses of vitamin D range from 800IU-2,000IU daily.¹⁴ It can take three to six months to reach a new steady-state of 25(OH)D levels.¹  There are certain circumstances, such as when a potent anti-resorptive is proposed (such as zoledronate or denosumab) where rapid correction with higher loading doses may be desirable.¹ There are various regimens to achieve this – more information can be found on the ROS and NICE Clinical Knowledge Summaries websites. Most of these regimens aim for a loading regimen of 280,000 to 300,000 IU over six to ten weeks (for example 4,000 IU/day over 10 weeks or 40,000IU/day over seven weeks) before moving to a long-term maintenance dose (800-2,000IU/day).¹ In the past large one-off loading doses of vitamin D were used, and these are now generally avoided in routine practice.

Vitamin D supplementation is largely safe when used within the suggested dose ranges and should be started within the community. However, the SACN cautions against the use of vitamin D in patients that have hypercalcaemia or are predisposed to hypercalcaemia (such as metastatic bone disease, lymphomas, granulomatous diseases such as sarcoidosis and tuberculosis), and those with history of nephrolithiasis, due to the increased risk of vitamin D toxicity.^11,13  The Joint Formulary Committee advises that such populations be referred to a specialist for treatment.¹⁴ Specialist input is also recommended for patients with malabsorption disorders who may require high-dose or intramuscular replacement¹ and for patients with severe liver/renal disease who may require active forms of vitamin D.^13,14,15 

Calcium intake should be optimised, preferably through dietary intake, and this can be assessed using online calculators.

Dr Zahra Ravat is NIHR Academic Clinical Fellow and Specialty Trainee in Endocrinology and Dr Zaki Hassan-Smith is Honorary Consultant Endocrinologist and Clinical Associate Professor at Aston University and University Hospitals Birmingham NHS Foundation Trust

References

1. Royal Osteoporosis Society. Vitamin D and Bone Health: A Practical Clinical Guideline for Patient Management. 2020
2. Aoun A, Maalouf J, Fahed M at al. When and How to Diagnose and Treat Vitamin D Deficiency in Adults: A Practical and Clinical Update. Journal of dietary supplements 2020;17(3):336-354
3. Hassan-Smith Z, Hewison M and Gittoes N. Effect of vitamin D deficiency in developed countries. British Medical Bulletin 2017;122(1):79-89
4. Kamwa V and Hassan-Smith Z. The inter-relationship between marginal vitamin D deficiency and muscle. Current opinion in endocrinology, diabetes, and obesity 2019;26(6):322-328
5. NICE. Vitamin D: supplement use in specific population groups [PH56]. 2017
6. UK Government. SACN vitamin D and health report. 2016
7. Giustina A, Bilezikian J, Adler R et al. Consensus Statement on Vitamin D Status Assessment and Supplementation: Whys, Whens, and Hows. Endocrine Reviews 2024;45(5):625-654
8. Kahwati L, LeBlanc E, Weberet R et al. Screening for Vitamin D Deficiency in Adults: Updated Evidence Report and Systematic Review for the US Preventive Services Task Force. JAMA 2021;325(14):1443-1463
9. Ross A, Taylor C, Yaktine A et al. Dietary Reference Intakes for Calcium and Vitamin D. National Academies Press (US) 2011
10. Ross A, Manson J, Abrams Set al. The 2011 report on dietary reference intakes for calcium and vitamin D from the Institute of Medicine: what clinicians need to know. The Journal of clinical endocrinology and metabolism 2011;96(1):53-58
11. Amrein K, Scherkl M, Hoffmann M et al. Vitamin D deficiency 2.0: an update on the current status worldwide. European Journal of Clinical Nutrition 2020;74(11):1498-1513
12. NICE Clinical Knowledge Summaries. Vitamin D deficiency in adults: Vitamin D supplements. 2022
13. Pludowski P, Holick M, Grant W et al. Vitamin D supplementation guidelines. The Journal of Steroid Biochemistry and Molecular Biology 2018;175:125-135
14. NICE. CKS. Scenario: Management of vitamin D deficiency or insufficiency. 2022
15. NHS Specialist Pharmacy Service. Vitamin D deficiency: treatment during pregnancy. 2025