Serum potassium refers to the amount of potassium ions in the blood, which is involved in many physiological functions of the body, but not the more the better, as there is a normal range of 3.5-5.5 mmol/L. If the level of potassium ions in the blood is lower than 3.5 mmol/L, the patient is in a state of hypokalemia, while if the level is higher than 5.5 mmol/L, the patient is suffering from hyperkalemia. If the potassium level in the blood is higher than 5.5 mmol/L, the patient is suffering from hyperkalemia. Both hypokalemia and hyperkalemia must be treated promptly because they can lead to sudden death and must be taken seriously. If the condition is mild, the patient can be treated in the endocrinology department, but if the condition is acute, the patient should be seen in the emergency department.