Deltius (Cholecalciferol 25,000 IU)
High-dose vitamin D3 capsule for treatment and prevention of vitamin D deficiency
Quick Facts About Deltius
Key Takeaways About Deltius
- High-dose vitamin D3: Deltius contains 25,000 IU of cholecalciferol per capsule, designed for intermittent dosing (weekly or monthly) rather than daily use
- Prescription only: Due to the high dose, Deltius requires a doctor's prescription and regular monitoring of blood calcium and 25(OH)D levels
- Essential for bone health: Vitamin D3 promotes calcium absorption from the gut and is crucial for maintaining strong bones and preventing osteoporosis and osteomalacia
- Watch for hypercalcemia: Taking too much vitamin D can raise blood calcium to dangerous levels, causing nausea, thirst, confusion, and kidney damage
- Drug interactions matter: Thiazide diuretics, digoxin, and corticosteroids can significantly interact with high-dose vitamin D therapy
What Is Deltius and What Is It Used For?
Deltius is a prescription medicine containing 25,000 IU of cholecalciferol (vitamin D3) in a hard capsule. It is used for the treatment and prevention of vitamin D deficiency in adults, particularly when higher intermittent doses are more practical than daily supplementation. Vitamin D is essential for calcium absorption, bone mineralization, immune function, and muscle strength.
Cholecalciferol, the active ingredient in Deltius, is the naturally occurring form of vitamin D that the human body produces in the skin upon exposure to ultraviolet B (UVB) sunlight. However, many people do not produce sufficient vitamin D from sunlight alone due to factors including geographical latitude, seasonal variation, darker skin pigmentation, limited sun exposure, use of sunscreen, aging, and obesity. In these populations, supplementation becomes necessary to prevent and treat deficiency.
Vitamin D deficiency is remarkably common worldwide. The World Health Organization and the Endocrine Society estimate that approximately 1 billion people globally have inadequate vitamin D levels, defined as serum 25-hydroxyvitamin D [25(OH)D] concentrations below 50 nmol/L (20 ng/mL). Severe deficiency, with levels below 25 nmol/L (10 ng/mL), affects an estimated 5-10% of the general population in northern latitudes and can lead to significant clinical consequences including osteomalacia in adults and rickets in children.
Once ingested, cholecalciferol undergoes a two-step metabolic activation process. First, it is hydroxylated in the liver to form calcifediol (25-hydroxyvitamin D or 25(OH)D), which is the primary circulating form measured in blood tests to assess vitamin D status. Second, calcifediol is further hydroxylated in the kidneys to form calcitriol (1,25-dihydroxyvitamin D), the biologically active hormone. Calcitriol binds to vitamin D receptors found in nearly every cell in the body and regulates the expression of over 200 genes involved in calcium and phosphorus homeostasis, cell differentiation, immune modulation, and inflammation control.
The high-dose formulation of Deltius (25,000 IU per capsule) is specifically designed for intermittent dosing regimens. Rather than taking a lower dose daily, patients may take one capsule weekly or monthly as directed by their physician. This approach has been shown in clinical trials to achieve equivalent serum 25(OH)D levels compared to daily dosing while improving medication adherence, particularly in elderly patients or those with complex medication regimens.
Primary Indications
- Vitamin D deficiency treatment: Rapid correction of confirmed deficiency (serum 25(OH)D below 25 nmol/L)
- Vitamin D insufficiency: Raising suboptimal levels (25(OH)D between 25-50 nmol/L) to the recommended range
- Osteoporosis prevention and treatment: As adjunctive therapy with calcium supplementation to maintain bone density
- Osteomalacia: Treatment of bone softening caused by severe vitamin D deficiency
- Malabsorption syndromes: Higher doses may be needed in patients with conditions affecting fat absorption (e.g., celiac disease, inflammatory bowel disease, cystic fibrosis)
- Hypoparathyroidism: Used alongside calcium and possibly calcitriol to manage low parathyroid hormone conditions
Vitamin D is a fat-soluble vitamin, meaning it is stored in body fat and the liver. Unlike water-soluble vitamins, excess vitamin D is not easily excreted and can accumulate to toxic levels. This is why the high-dose Deltius capsules require a prescription and medical monitoring. Your doctor will check your blood calcium and 25(OH)D levels before starting treatment and at regular intervals during therapy.
What Should You Know Before Taking Deltius?
Before taking Deltius, inform your doctor about all medical conditions, especially kidney disease, high calcium levels, kidney stones, sarcoidosis, or other granulomatous diseases. Deltius should not be taken if you have hypercalcemia, hypervitaminosis D, or severe kidney impairment. Pregnancy and breastfeeding require careful medical supervision.
Contraindications
You must not take Deltius if you have any of the following conditions, as the high dose of vitamin D could worsen these conditions and lead to potentially serious complications:
- Hypercalcemia: Elevated blood calcium levels (serum calcium above 2.6 mmol/L). Vitamin D increases calcium absorption and could raise levels further, potentially causing cardiac arrhythmias, kidney damage, and calcification of soft tissues.
- Hypervitaminosis D: Already elevated vitamin D levels in the blood, indicating existing toxicity or overdose from any source of vitamin D supplementation.
- Hypercalciuria: Excessive calcium excretion in the urine, which increases the risk of kidney stone formation when vitamin D is supplemented.
- Nephrolithiasis: Current calcium-containing kidney stones, as vitamin D can promote further stone formation by increasing urinary calcium excretion.
- Severe renal impairment: Advanced chronic kidney disease (estimated GFR below 15 mL/min) where the kidneys cannot properly metabolize vitamin D, and direct calcitriol or alfacalcidol may be more appropriate alternatives.
- Known hypersensitivity: Allergy to cholecalciferol or any of the excipients in the capsule formulation, including peanut oil or soya (if present in specific formulations).
Warnings and Precautions
Use Deltius with particular caution and under close medical supervision if you have any of the following conditions. Your doctor may need to adjust your dose or monitor you more frequently:
Sarcoidosis and other granulomatous diseases: In these conditions, immune cells (macrophages) within granulomas produce calcitriol independently of normal regulatory mechanisms. This unregulated extra-renal production of active vitamin D can lead to hypercalcemia even with modest supplementation. Patients with sarcoidosis, tuberculosis, berylliosis, or certain lymphomas require careful dose adjustment and frequent calcium monitoring.
Kidney disease: Patients with chronic kidney disease stages 3-4 (moderate to severe impairment) have reduced ability to convert calcifediol to active calcitriol. While they may still benefit from cholecalciferol supplementation to maintain adequate 25(OH)D levels, they require careful monitoring and may need specialist nephrology input. In these patients, phosphate levels should also be monitored as vitamin D can increase phosphorus absorption.
Cardiac conditions: High calcium levels caused by excessive vitamin D can affect cardiac conductivity and increase the toxicity of cardiac glycosides such as digoxin. Patients taking digoxin who also receive high-dose vitamin D must have their serum calcium levels monitored particularly closely to prevent potentially dangerous cardiac arrhythmias.
Immobilised patients: Prolonged immobility increases the risk of hypercalcemia because bone turnover is accelerated during bed rest. Patients who are bedridden or have limited mobility may require lower doses and more frequent monitoring when taking Deltius.
Do not exceed the prescribed dose of Deltius. Vitamin D toxicity (hypervitaminosis D) from excessive supplementation can cause severe hypercalcemia with symptoms including persistent nausea, vomiting, abdominal pain, extreme thirst, frequent urination, muscle weakness, bone pain, confusion, and kidney failure. If you experience any of these symptoms, stop taking Deltius and contact your doctor immediately. Long-term toxicity can lead to irreversible kidney damage, cardiovascular calcification, and potentially life-threatening complications.
Pregnancy and Breastfeeding
Adequate vitamin D status during pregnancy is important for both maternal and fetal health. Vitamin D deficiency during pregnancy has been associated with an increased risk of pre-eclampsia, gestational diabetes, preterm birth, and low birth weight. However, the high dose in Deltius (25,000 IU per capsule) requires careful consideration during pregnancy.
Animal studies have shown that very high doses of vitamin D can cause fetal abnormalities, including skeletal malformations and organ calcification. While the clinical relevance of these findings to humans at therapeutic doses is uncertain, the European Medicines Agency (EMA) advises that daily vitamin D intake during pregnancy should generally not exceed 4,000 IU (100 micrograms) unless specifically directed by a physician for documented deficiency. If your doctor prescribes Deltius during pregnancy, the dosing interval will be carefully adjusted to avoid sustained high serum levels.
Vitamin D and its metabolites are excreted in breast milk, though the amounts transferred to the infant are generally small relative to the infant's requirements. Breastfeeding mothers taking Deltius should be monitored, and their infants may also need monitoring if the mother is receiving loading doses. Excessive maternal supplementation could lead to hypercalcemia in the nursing infant, presenting as poor feeding, irritability, and failure to thrive.
How Does Deltius Interact with Other Drugs?
Deltius can interact with several common medications. Thiazide diuretics increase the risk of hypercalcemia, cardiac glycosides like digoxin become more toxic at higher calcium levels, and fat-binding agents reduce vitamin D absorption. Anticonvulsants and corticosteroids can accelerate vitamin D metabolism, potentially requiring dose adjustments.
Drug interactions with high-dose vitamin D are clinically significant because cholecalciferol alters calcium homeostasis, which in turn affects the pharmacology of multiple drug classes. Understanding these interactions is essential for safe prescribing and patient management. Always inform your doctor and pharmacist about all medications, supplements, and herbal products you are taking before starting Deltius.
Major Interactions
The following interactions are considered clinically significant and require dose adjustment, additional monitoring, or avoidance of the combination:
| Drug / Drug Class | Interaction Mechanism | Clinical Consequence | Management |
|---|---|---|---|
| Thiazide diuretics (hydrochlorothiazide, indapamide) | Thiazides reduce urinary calcium excretion, increasing serum calcium | Significantly increased risk of hypercalcemia | Monitor serum calcium regularly; reduce vitamin D dose if needed |
| Cardiac glycosides (digoxin, digitoxin) | Hypercalcemia potentiates cardiac glycoside toxicity | Risk of life-threatening cardiac arrhythmias | Monitor serum calcium and digoxin levels closely; ECG monitoring |
| Calcium supplements | Additive increase in total calcium load | Hypercalcemia and hypercalciuria | Coordinate total calcium intake; monitor levels |
| Other vitamin D products | Additive vitamin D exposure from multiple sources | Hypervitaminosis D and hypercalcemia | Account for all vitamin D sources including fortified foods |
Minor Interactions
The following interactions may reduce the effectiveness of Deltius or require awareness but are generally manageable with appropriate monitoring:
| Drug / Drug Class | Interaction Mechanism | Clinical Consequence | Management |
|---|---|---|---|
| Orlistat | Inhibits fat absorption, reducing vitamin D uptake | Decreased vitamin D levels | Take Deltius at least 2 hours apart from orlistat |
| Cholestyramine, colestipol | Bile acid sequestrants bind fat-soluble vitamins | Reduced vitamin D absorption | Take Deltius at least 4 hours before or after |
| Phenytoin, phenobarbital, carbamazepine | Induce CYP450 enzymes that metabolize vitamin D | Accelerated vitamin D inactivation; may need higher doses | Monitor 25(OH)D levels; adjust dose accordingly |
| Rifampicin | Potent CYP3A4/CYP24A1 inducer | Significantly accelerated vitamin D catabolism | May need substantially higher vitamin D doses |
| Glucocorticoids (prednisolone, dexamethasone) | Impair calcium absorption and increase vitamin D catabolism | Reduced effectiveness of vitamin D supplementation | Higher vitamin D doses often needed; monitor bone density |
| Ketoconazole | Inhibits CYP enzymes involved in vitamin D activation | Reduced formation of active vitamin D metabolites | Monitor 25(OH)D and calcium levels |
What Is the Correct Dosage of Deltius?
Deltius 25,000 IU is typically prescribed as one capsule per week for 6-8 weeks to correct deficiency (loading phase), followed by one capsule per month for maintenance. The exact regimen depends on the severity of deficiency, individual patient factors, and blood test results. Never take Deltius daily unless specifically instructed by your physician.
Dosing of high-dose vitamin D supplements like Deltius must be individualised based on the patient's baseline serum 25(OH)D level, clinical situation, body weight, and response to treatment. The following are general guidelines based on recommendations from the Endocrine Society, NICE, and European guidelines. Your doctor will determine the most appropriate regimen for your specific situation.
Adults
Loading Phase (Deficiency Correction)
For confirmed vitamin D deficiency (serum 25(OH)D below 25 nmol/L or 10 ng/mL):
- Standard loading: One capsule (25,000 IU) once weekly for 6-8 weeks, providing a total loading dose of approximately 150,000-200,000 IU
- Severe deficiency: Your doctor may prescribe one capsule weekly for up to 12 weeks depending on the degree of deficiency and clinical response
- Recheck serum 25(OH)D levels 4-6 weeks after completing the loading phase to confirm adequate repletion
Maintenance Phase
After successful correction of deficiency:
- Standard maintenance: One capsule (25,000 IU) once monthly
- Alternative: One capsule every 2 weeks if monthly dosing is insufficient to maintain target levels
- Target serum 25(OH)D level: 50-75 nmol/L (20-30 ng/mL) for most patients; up to 100 nmol/L for certain clinical situations
- Monitor serum 25(OH)D and calcium at least annually during long-term maintenance therapy
Children
Paediatric Use
Deltius 25,000 IU capsules are generally not recommended for children and adolescents under 18 years due to the high dose per capsule. Lower-strength formulations (drops, tablets, or oral solutions) are preferred for paediatric patients to allow more precise dose adjustment. However, in specific clinical situations (e.g., adolescent patients with severe deficiency or malabsorption), a physician may prescribe Deltius under close supervision:
- Adolescents (12-17 years) with severe deficiency: Dosing at the physician's discretion, typically not exceeding adult loading doses
- Children under 12 years: Use of lower-strength formulations is strongly recommended
Elderly
Geriatric Dosing Considerations
Elderly patients (over 65 years) are at particularly high risk of vitamin D deficiency due to reduced skin synthesis, decreased renal hydroxylation capacity, limited sun exposure, and dietary inadequacy. However, they also have an increased susceptibility to hypercalcemia. Dosing considerations include:
- Loading phase: Same as adults, but with more frequent calcium monitoring (every 2-4 weeks during loading)
- Maintenance: One capsule monthly is typically appropriate; monitor renal function and calcium
- Patients with renal impairment (common in the elderly) may require dose adjustment
- Consider risk of falls: adequate vitamin D levels (above 50 nmol/L) are associated with reduced fall risk in elderly populations
Missed Dose
If you forget to take your scheduled dose of Deltius, take it as soon as you remember. However, if it is almost time for your next scheduled dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to compensate for a forgotten capsule. Because vitamin D is stored in body fat and has a long half-life (approximately 2-3 months for the 25(OH)D metabolite), missing an occasional dose is unlikely to cause significant clinical consequences, though consistently missing doses will result in subtherapeutic levels over time.
Overdose
Vitamin D overdose is a medical emergency. Acute overdose or chronic excessive intake of Deltius can lead to severe hypercalcemia with potentially life-threatening consequences. Symptoms of overdose typically develop over days to weeks and include:
- Early symptoms: Nausea, vomiting, loss of appetite, constipation, abdominal pain, extreme thirst (polydipsia), frequent urination (polyuria)
- Progressive symptoms: Dehydration, muscle weakness, bone pain, fatigue, drowsiness, confusion, headache
- Severe complications: Cardiac arrhythmias, acute kidney injury, nephrocalcinosis (calcium deposits in kidneys), metastatic calcification of blood vessels and organs, pancreatitis, and in extreme cases, coma and death
If overdose is suspected, stop Deltius immediately and seek emergency medical attention. Treatment involves aggressive intravenous fluid hydration, loop diuretics (furosemide) to promote calcium excretion, and potentially corticosteroids, calcitonin, or bisphosphonates to reduce serum calcium levels. Serum calcium, phosphate, renal function, and ECG should be monitored intensively.
What Are the Side Effects of Deltius?
When taken at the prescribed dose, Deltius is generally well tolerated. The most clinically significant adverse effect is hypercalcemia, which results from excessive vitamin D intake rather than an idiosyncratic reaction. Allergic reactions are very rare. Side effect frequency is dose-dependent, and most adverse effects resolve upon dose reduction or discontinuation.
Like all medicines, Deltius can cause side effects, although not everybody gets them. Most side effects associated with cholecalciferol at the 25,000 IU dose are related to its primary pharmacological action of increasing calcium absorption. When serum calcium levels remain within the normal range, side effects are uncommon. The risk of adverse effects increases with higher cumulative doses or in patients with predisposing conditions such as those listed in the contraindications and warnings sections above.
The frequency categories below are based on post-marketing surveillance data, clinical trial experience, and pharmacovigilance reports for high-dose cholecalciferol preparations. Individual susceptibility varies, and patients should report any unusual symptoms to their healthcare provider.
Common (affects 1 to 10 in every 100 patients)
- Hypercalcemia (elevated blood calcium) when doses are not adequately monitored
- Hypercalciuria (excessive calcium in urine)
- Nausea
- Constipation
- Abdominal pain
Uncommon (affects 1 to 10 in every 1,000 patients)
- Polydipsia (excessive thirst)
- Polyuria (frequent urination)
- Headache
- Fatigue and drowsiness
- Muscle weakness
- Loss of appetite
- Metallic taste in the mouth
Rare (affects 1 to 10 in every 10,000 patients)
- Allergic skin reactions (rash, urticaria, pruritus)
- Nephrolithiasis (kidney stones)
- Nephrocalcinosis (calcium deposits in kidneys)
- Soft tissue calcification (with prolonged excessive dosing)
- Cardiac arrhythmias (secondary to hypercalcemia)
- Pancreatitis (associated with severe hypercalcemia)
- Anaphylactic reaction (extremely rare; related to excipients)
Contact your healthcare provider promptly if you experience persistent nausea or vomiting, excessive thirst, frequent urination, severe constipation, confusion, muscle weakness, or bone pain while taking Deltius. These may be signs of elevated calcium levels requiring dose adjustment or temporary discontinuation. Seek immediate medical attention if you develop signs of a severe allergic reaction including difficulty breathing, swelling of the face, lips, tongue, or throat, or a widespread skin rash.
How Should You Store Deltius?
Store Deltius capsules below 25°C (77°F) in the original packaging to protect from light and moisture. Do not freeze. Keep out of sight and reach of children. Do not use after the expiry date stated on the packaging.
Proper storage of Deltius is essential to maintain the potency and safety of the cholecalciferol contained in each capsule. Vitamin D3 is sensitive to degradation by light, heat, and moisture, and improper storage can reduce the active ingredient content over time, leading to subtherapeutic doses.
Keep the capsules in the original blister packaging until immediately before use. This protects them from ambient light and humidity which can accelerate chemical degradation of cholecalciferol. Do not store Deltius in the bathroom or near a sink, as the humidity and temperature fluctuations common in these environments can affect the product's stability.
The expiry date printed on the outer carton and blister packs refers to the last day of that month. Do not take Deltius after this date. Expired vitamin D supplements may have reduced potency and could potentially contain degradation products, although no specific safety concerns have been identified with expired cholecalciferol preparations.
Dispose of unused or expired Deltius capsules responsibly. Do not throw them in household waste or flush them down the toilet, as pharmaceutical waste can contaminate water supplies and the environment. Return unused medicines to your pharmacy for appropriate disposal through designated pharmaceutical waste collection programmes.
What Does Deltius Contain?
Each Deltius hard capsule contains 25,000 IU (625 micrograms) of cholecalciferol (vitamin D3) as the active substance. The capsule also contains excipients including medium-chain triglycerides (MCT oil) and other inactive ingredients necessary for the formulation.
The active ingredient, cholecalciferol, is identical to the vitamin D3 naturally produced in human skin upon UVB exposure. It is a secosteroid compound with the chemical name (3S,5Z,7E)-9,10-secocholesta-5,7,10(19)-trien-3-ol, and a molecular weight of 384.64 g/mol. Cholecalciferol is practically insoluble in water but soluble in fats and organic solvents, which is why it is formulated in oil-based capsules to enhance bioavailability.
Active Substance
- Cholecalciferol (Vitamin D3): 25,000 IU (equivalent to 625 micrograms) per capsule
Excipients (Inactive Ingredients)
The following excipients are typically present in the Deltius capsule formulation. The exact composition may vary slightly between manufacturers and batches. Check the patient information leaflet in your specific packaging for the definitive list:
- Medium-chain triglycerides (MCT oil): Serves as the oily vehicle to dissolve cholecalciferol and enhance gastrointestinal absorption
- Gelatin: Forms the hard capsule shell (note: not suitable for vegetarians or vegans)
- Glycerol: Used as a plasticiser in the capsule shell to maintain flexibility
- Titanium dioxide (E171): White colourant used in the capsule shell (note: the use of titanium dioxide in food and medicines is under ongoing regulatory review in some jurisdictions)
- Iron oxide yellow (E172): Colourant that may be present in the capsule shell
- Butylated hydroxytoluene (BHT): Antioxidant to prevent degradation of cholecalciferol
Deltius capsules contain gelatin and may contain traces of soya depending on the specific formulation. Patients with known allergies to soya, peanuts, or gelatin should consult their pharmacist or doctor before taking Deltius. Alternative vitamin D formulations (drops, oral solution, or vegetarian capsules) may be available for patients with specific dietary requirements or allergies.
Frequently Asked Questions About Deltius
The main difference is the dose. Deltius contains 25,000 IU of vitamin D3 per capsule, which is significantly higher than typical over-the-counter supplements that contain 400-2,000 IU per dose. This high dose means Deltius is designed for intermittent use (weekly or monthly) rather than daily supplementation. Because of the risk of toxicity at high doses, Deltius is a prescription-only medicine requiring blood test monitoring, whereas lower-dose supplements are available without prescription. Both contain the same active substance, cholecalciferol (vitamin D3).
Serum 25(OH)D levels typically begin rising within 1-2 weeks of starting Deltius. However, reaching optimal levels usually takes 6-8 weeks of weekly loading doses. The speed of response depends on the severity of your initial deficiency, your body weight (higher body weight requires more vitamin D due to its fat-soluble nature), and individual factors such as gut absorption capacity. Your doctor will typically recheck your blood levels 4-6 weeks after completing the loading phase to assess your response.
Yes, and in fact it is recommended to take Deltius with a meal containing some fat. Vitamin D3 is a fat-soluble vitamin, and its absorption from the gastrointestinal tract is significantly enhanced when taken with dietary fat. Studies have shown that taking vitamin D with a fat-containing meal can increase absorption by up to 50% compared to taking it on an empty stomach. A meal containing healthy fats such as olive oil, avocado, nuts, or cheese is ideal. Swallow the capsule whole with a glass of water.
This depends on your individual circumstances. Vitamin D enhances calcium absorption from the gut, so adequate dietary calcium intake is important during Deltius therapy. If your diet provides sufficient calcium (approximately 700-1,200 mg per day from dairy products, leafy greens, fortified foods, etc.), additional calcium supplements may not be necessary. However, if your doctor has identified calcium deficiency or if you are being treated for osteoporosis, a combined approach with calcium supplementation is often recommended. Your doctor will advise you based on your blood test results and dietary assessment.
Your doctor will typically order the following blood tests: Serum 25(OH)D to measure your vitamin D level (checked before starting, 4-6 weeks after loading, and then at least annually during maintenance). Serum calcium should be monitored before starting, during the loading phase (every 2-4 weeks in high-risk patients), and periodically during maintenance. Renal function tests (creatinine and eGFR) assess kidney health, which affects vitamin D metabolism. Serum phosphate may be checked in patients with kidney disease. Additional tests such as parathyroid hormone (PTH) may be requested to assess the underlying cause of deficiency and response to treatment.
Vitamin D is important during pregnancy, but the high dose in Deltius (25,000 IU per capsule) requires careful medical supervision. Excessive vitamin D during pregnancy can cause hypercalcemia in the mother, which may affect fetal development. If your doctor determines that high-dose vitamin D supplementation is needed during pregnancy, the dosing interval will be carefully calculated to keep average daily intake within safe limits (generally not exceeding 4,000 IU per day). During breastfeeding, vitamin D is excreted in breast milk, and the infant should also be monitored. Lower-dose daily formulations are generally preferred during pregnancy and breastfeeding unless your doctor decides otherwise.
References
This article is based on the following peer-reviewed sources and authoritative clinical guidelines:
- Holick MF, Binkley NC, Bischoff-Ferrari HA, et al. Evaluation, Treatment, and Prevention of Vitamin D Deficiency: an Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2011;96(7):1911-1930. doi:10.1210/jc.2011-0385
- Martineau AR, Jolliffe DA, Hooper RL, et al. Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data. BMJ. 2017;356:i6583. doi:10.1136/bmj.i6583
- NICE Clinical Knowledge Summary. Vitamin D deficiency in adults - treatment and prevention. National Institute for Health and Care Excellence. Updated 2024.
- Bouillon R, Marcocci C, Carmeliet G, et al. Skeletal and Extraskeletal Actions of Vitamin D: Current Evidence and Outstanding Questions. Endocr Rev. 2019;40(4):1109-1151. doi:10.1210/er.2018-00126
- European Medicines Agency. Cholecalciferol Summary of Product Characteristics (SmPC). EMA. Accessed 2026.
- World Health Organization. Vitamin D supplementation in adults. WHO e-Library of Evidence for Nutrition Actions (eLENA). 2024.
- Cashman KD, Dowling KG, Skrabakova Z, et al. Vitamin D deficiency in Europe: pandemic? Am J Clin Nutr. 2016;103(4):1033-1044. doi:10.3945/ajcn.115.120873
- Bischoff-Ferrari HA, Dawson-Hughes B, Orav EJ, et al. Monthly High-Dose Vitamin D Treatment for the Prevention of Functional Decline. JAMA Intern Med. 2016;176(2):175-183. doi:10.1001/jamainternmed.2015.7148
- Ross AC, Manson JE, Abrams SA, et al. The 2011 Report on Dietary Reference Intakes for Calcium and Vitamin D from the Institute of Medicine: What Clinicians Need to Know. J Clin Endocrinol Metab. 2011;96(1):53-58. doi:10.1210/jc.2010-2704
- British National Formulary (BNF). Colecalciferol monograph. NICE Evidence Services. Updated 2025.
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