Electrolyte tests are designed to check the balance of potassium, sodium and chloride in the body’s cells. The tests include potassium, sodium, chloride, calcium, phosphorus and magnesium in the blood, with the most important ones being potassium, sodium and calcium. 1. Blood potassium: The blood potassium test can reflect the changes in the concentration of potassium ions in the extracellular fluid, and is suitable for patients suffering from high blood pressure, cardiac arrhythmia and kidney failure. 2. Blood Sodium: Blood serum can maintain the volume of extracellular fluid and acid-base balance, and has the function of maintaining the normal stress of muscles and nerves, mostly in the form of sodium chloride. Blood sodium test is suitable for patients with water electrolyte balance disorders and renal diseases. 3. Calcium: Calcium in the blood exists in the form of protein-bound calcium, complex calcium and free calcium, which accounts for only 1% of the body’s calcium content. Calcium is measured in patients with abnormal growth and malabsorption, parathyroid disorders, and cardiac disorders. Patients who experience abnormalities in the test should be diagnosed and treated under the direction of a physician.