Vitamin D (Supplement)
Brand names: D-Vit, Devit, Vitamine D3, Ergoferon D
Fat-soluble vitamin / hormone precursor
Vitamin D deficiency is one of the most prevalent nutritional deficiencies globally, particularly in Gulf countries where sun avoidance is common. Supplementation restores bone health, supports immune function, and corrects documented deficiency.
Drug Class
Fat-soluble vitamin / hormone precursor
Category
Vitamins & Supplements
Forms Available
Oral drops (400 IU, 1000 IU per drop), Tablets and capsules (400 IU, 1000 IU, 2000 IU, 4000 IU)
How It Works
Vitamin D3 (cholecalciferol) is converted in the liver to 25-hydroxyvitamin D (the storage form measured by blood tests), and then in the kidneys to 1,25-dihydroxyvitamin D (calcitriol) — the active hormone. Calcitriol enhances calcium absorption from the gut, supports bone mineralisation, modulates the immune system, and influences gene expression in dozens of tissue types.
What It's Used For
- Vitamin D deficiency and insufficiency
- Prevention and treatment of osteoporosis (with calcium)
- Rickets in children
- Osteomalacia in adults
- Hypoparathyroidism
- Supported immune function
Available Forms
Side Effects
Common Side Effects
- At recommended doses: virtually none
- With excessive supplementation: nausea, constipation, weakness
Serious Side Effects
- Vitamin D toxicity (hypervitaminosis D) — from very high supplementation doses over time; causes hypercalcaemia
- Hypercalcaemia: nausea, vomiting, confusion, kidney stones, cardiac arrhythmia
- Toxicity essentially never occurs from sunlight or dietary sources alone
Drug Interactions
- Thiazide diuretics — increase hypercalcaemia risk if combined with vitamin D
- Digoxin — hypercalcaemia sensitises the heart to digoxin toxicity
- Orlistat, cholestyramine — reduce vitamin D absorption
When to Avoid
- Hypercalcaemia or hypercalciuria
- Sarcoidosis and other granulomatous diseases — increased risk of hypercalcaemia
- Certain lymphomas
Patient Tips
- Test your 25-OH vitamin D level before starting high-dose supplementation
- Deficiency: < 20 ng/mL (50 nmol/L); Insufficiency: 20–30 ng/mL; Optimal: 30–60 ng/mL
- D3 (cholecalciferol) is more effective at raising serum 25-OH vitamin D than D2 (ergocalciferol)
- Take vitamin D with a meal containing fat — it is fat-soluble and absorption is improved with dietary fat
- Typical maintenance supplementation: 1000–2000 IU daily; correction doses: 4000–10,000 IU daily for 8–12 weeks
- Retest after 3 months of supplementation to confirm your levels have reached target
Vitamin D deficiency in the Gulf region
Despite abundant sunshine, vitamin D deficiency is paradoxically very common in Gulf countries. The combination of sun avoidance due to heat, indoor lifestyles, clothing coverage, dark skin pigmentation (which requires longer sun exposure to produce D3), and sunscreen use means that many UAE residents have 25-OH vitamin D levels below 20 ng/mL.
Routine screening and supplementation are commonly recommended by UAE healthcare providers for this reason.
Vitamin D and COVID-19 / immunity
Observational studies during the COVID-19 pandemic noted associations between vitamin D deficiency and worse outcomes. While this likely reflects the general importance of vitamin D in immune regulation, supplementation trials have not consistently shown clear protection against infection in vitamin D-sufficient individuals.
Correcting documented deficiency is clearly beneficial. Taking very high doses beyond correction offers no proven additional benefit and raises toxicity risk.
Related Medicines
Medical disclaimer
This page is for educational reference only. Always follow the dosage and instructions given by your prescriber or pharmacist. Do not start, stop, or change medicines without medical advice.
Reviewed 2026-06-01 · Looms Medical Team