Description: Defrol 40000 IU is a high-dose Vitamin D3 (cholecalciferol) supplement used to treat severe vitamin D deficiency or to correct deficiencies caused by conditions like osteoporosis, rickets, or chronic kidney disease. Vitamin D is essential for proper calcium and phosphorus absorption in the body, which helps maintain bone health and supports immune function. This high-dose formulation, typically used when standard doses are insufficient, is often prescribed in cases where patients have difficulty absorbing vitamin D from their diet or sunlight or those with certain health conditions that interfere with vitamin D metabolism. As 40000 IU is a very high dose, it is important to use this under medical supervision to prevent vitamin D toxicity, which can lead to harmful effects like hypercalcemia (high calcium levels in the blood).