The normal value of blood potassium is 3.5-5.5 mmol/L. When the blood potassium concentration is lower than 3.5 mmol/L, it is considered hypokalemia and requires potassium supplementation. Oral potassium supplementation is relatively safer and simpler than intravenous potassium supplementation, and is not limited by the concentration and speed of potassium supplementation. The principles of oral potassium supplementation are as follows: First, potassium supplementation should be given only when the blood potassium concentration is lower than 3.5 mmol/L. Second, oral potassium supplementation can be chosen from a wide range of potassium concentrations. The oral potassium supplementation can be done with oral potassium chloride tablets or with 10% potassium chloride solution. The oral dose can be decided according to the degree of potassium reduction. During the process of oral potassium supplementation, the urine volume, kidney function and blood potassium concentration should be monitored regularly to avoid hyperkalemia. Fourth, attention can be paid to consuming more foods with high potassium content and to finding the cause of hyperkalemia.