The normal range for blood potassium is 3. 5 ~ 5. 5 mmol/L. Potassium ions are the major intracellular cation, and about 98% of blood potassium is distributed in the intracellular fluid, with only a small fraction of potassium ions distributed in the extracellular fluid. The blood potassium level measured clinically actually refers to the concentration of potassium ions in the extracellular fluid. However, since potassium ions can be exchanged dynamically between inside and outside the cell and remain at a certain stable level, changes in the blood potassium level to a certain extent also reflect changes in the concentration of potassium ions in the intracellular fluid. The normal value of blood potassium ranges from 3.5 to 5.5 mmol/L. Below 3.5 mmol/L is considered hypokalemia, while above 5.5 mmol/L is considered hyperkalemia, and both hypokalemia and hyperkalemia have great effects on the human body. Therefore, close monitoring of blood potassium levels is required in patients with abnormalities.