In patients with chronic renal failure, hyperphosphatemia usually occurs in the late stage of the disease, with blood phosphorus greater than 1.61 mmol/L, and greater than 1.9 mmol/L in children, and its effects on the body: inhibition of renal tubular 1a-hydroxylase activity, resulting in impaired metabolism of vitamin D, inhibition of osteocalcin uptake, and ultimately, the emergence of renal osteodystrophy. Since ([Ca] × [P]) is 30 to 40, when ([Ca] × [P]) > 40, calcium and phosphorus are deposited in bone tissue in the form of bone salts; if ([Ca] × [P]) < 35, it prevents bone calcification, and even dissolves bone salts, affecting osteogenesis. Therefore, high phosphorus leads to ectopic calcification, appearing: (1) kidney stones; (2) skin calcification, skin itching; other causes of high blood phosphorus is seen in: hypoparathyroidism, vitamin D poisoning, chemotherapy is the cells release a large number of phosphorus ions. 2. Hypocalcemia: less than 2.2mmol/L, the reason is similar to high phosphorus, the effect on the body: 1) on neuromuscular: increased excitability, resulting in twitching of hands and feet, muscle spasm; 2) on bone metabolism disorders: children lead to rickets, adult osteochondrosis, fibrous osteitis, osteoporosis, etc.; 3) on the myocardium: myocardial excitability, transmission is elevated, but the decrease in the force of contraction. In addition, the calculation method of calcium-phosphorus product is given: the unit of blood calcium and blood phosphorus is molar concentration (mol/L), the original unit is percent milligram (mg/dl), calcium-phosphorus product is used in the unit of percent milligrams, therefore, it is necessary to convert the molar concentration to percent milligrams. The relationship between the two is: calcium: 1mg/dl = 0.25mmol / L, that is, 1mmol / L = 4mg / dl; phosphorus: 1mg / dl = 0.3229mmol / L, that is, 1mmol / L = 3.1mg / dl. So, when the mmol / l calculation can be: 12.4XCaXP, that is, the product of the two ([Ca] x [P]) for 30-40. ～When calculated directly, the calcium-phosphorus product is less than 4.52, which is normal. The Expert Consensus on the Rational Application of Activated Vitamin D in Chronic Kidney Disease Secondary to Hyperparathyroidism (Revised Edition) points out that the target calcium-phosphorus product of corrected serum total calcium, blood phosphorus, and whole-segment parathyroid hormone (iPTH) levels of patients with CKD should be <55mg2/dl2. Common Adverse Reactions of Activated Vitamin D and its Countermeasures 1. Common adverse reactions: Elevation of blood calcium and blood phosphorus. In addition, improper application of active vitamin D may cause excessive inhibition of iPTH, which may lead to the development of power-deficient bone disease. 2. Countermeasures: (1) Closely monitor blood calcium, phosphorus, iPTH and calcium-phosphorus product levels. (2) If there is elevated blood phosphorus, first actively reduce phosphorus. (3) If blood calcium > 2.54 mmol/L (10.2 mg/ml): ① should reduce or discontinue the use of calcium-containing phosphorus binding agent; when possible, the use of calcium-free phosphorus binding agent; ② severe hypercalcemia should be reduced or discontinued active vitamin D, and then restarted until the blood calcium to return to normal; ③ dialysis patients, according to the level of calcium can be used in a low-calcium dialysis solution (1.25 mmol / L or lower) dialysis, and the patient’s symptoms and blood pressure should be closely monitored during dialysis. (4) It is recommended that active vitamin D be administered at night before sleep when the intestinal calcium load is lowest.