The efficacy and role of vitamin D are as follows: prevention and treatment of vitamin D deficiency, treatment of chronic hypocalcemia and hypophosphatemia, treatment of acute, chronic and potentially post-surgical tetany and idiopathic tetany. 1. Prevention and treatment of vitamin D deficiency. Such as absolute vegetarians, patients with parenteral nutrition, pancreatic insufficiency with malabsorption syndrome, hepatobiliary diseases (liver function impairment, cirrhosis, obstructive jaundice), small intestinal disorders (lipid diarrhea, restrictive enteritis, long-term diarrhea), gastrectomy and so on. 2. It is used in the treatment of chronic hypocalcemia, hypophosphatemia, rickets and osteochondrosis with chronic renal insufficiency, familial hypophosphatemia and hypoparathyroidism (postoperative, idiopathic or pseudohypoparathyroidism). 3. Vitamin D is used in the treatment of acute, chronic and potentially post-surgical tetany and idiopathic tetany. Constipation, diarrhea, persistent headache, loss of appetite, metallic taste in the mouth, nausea and vomiting, thirst, fatigue, weakness, bone pain, cloudy urine, convulsions, hypertension, increased sensitivity of the eyes to light stimuli, cardiac arrhythmia, occasional psychiatric abnormalities, itching of the skin, myalgia, severe abdominal pain (sometimes misdiagnosed as pancreatitis), nocturnal polyuria, and weight loss can be seen as adverse reactions to taking Vitamin D. Vitamin D is contraindicated in patients with hypercalcemia, hypervitaminosis D, hyperphosphatemia with renal rickets, and should be taken in accordance with medical advice.