India has one of the highest rates of Vitamin D deficiency in the world despite being a sun-drenched country. For Indian doctors, Vitamin D has become one of the most-ordered tests and most-discussed topics in OPD. This guide covers what the evidence actually supports in 2026. Practical Vitamin D Guide for Indian Doctors (2026) 1. Why Vitamin D Deficiency Is So Common in India Darker skin → more melanin → less UV-B absorption → longer sun exposure needed. Urban, indoor lifestyles and cosmetic sun avoidance. Full-body / covering clothing limiting exposed skin. High air pollution reducing UV-B penetration. Predominantly vegetarian diets; low oily fish intake; minimal fortified foods. 2. Vitamin D Testing: When and How to Interpret Results Who Should Be Tested? Symptomatic patients: fatigue, myalgia, bone pain, depression, recurrent infections. High-risk groups: elderly, pregnant/lactating women, exclusively breastfed infants, patients with T2DM, CKD, malabsorption, or on long-term steroids/anticonvulsants. Incidental: routine health check-up in Indian adults with metabolic syndrome, obesity, or autoimmune conditions. 25(OH)D Levels and Classification Deficiency: < 20 ng/mL. Treat. Insufficiency: 20–29 ng/mL. Supplement in high-risk patients. Optimal: 30–60 ng/mL. Target for most patients. Toxicity risk: > 100–150 ng/mL with high-dose supplements. Rare from sun exposure alone. 3. Treatment Protocols for Indian Patients Repletion Phase (Loading) For levels < 20 ng/mL: cholecalciferol (D3) 60,000 IU once weekly × 8–12 weeks. D3 is preferred over D2 (ergocalciferol) for superior bioavailability and more sustained rise in 25(OH)D. Oral sachet formulations (60,000 IU) widely available in India; easily prescribed and affordable. Maintenance Phase After repletion: 1,000–2,000 IU daily or 60,000 IU monthly indefinitely for high-risk individuals. Co-supplementation with calcium (500–1,000 mg/day) only if dietary intake is inadequate; avoid routine calcium supplements in patients with adequate dietary intake. 4. Special Populations Pregnancy: 2,000 IU daily throughout pregnancy; check levels at booking and in 3rd trimester. Infants (breastfed): 400 IU/day from birth; 800–1,000 IU/day if mother is deficient. CKD: Use native vitamin D (cholecalciferol) to correct nutritional deficiency; active vitamin D (calcitriol/alfacalcidol) is added when secondary hyperparathyroidism develops — do not substitute one for the other. Malabsorption (IBD, bariatric surgery): Higher doses needed (6,000–10,000 IU/day); monitor levels closely. 5. Common Clinical Questions Does Vitamin D supplementation prevent COVID-19 or infections? Evidence is weak for direct infection prevention. Correction of deficiency is still warranted given its role in immune function and musculoskeletal health. What if level rises above 100 ng/mL? Stop supplementation. Recheck in 4–6 weeks. Check serum calcium. Toxicity (hypercalcaemia) is rare but possible at persistently very high levels. When to recheck 25(OH)D after starting treatment? Recheck at 8–12 weeks after completing the repletion phase. Once on maintenance, annual monitoring is sufficient in most patients.