When severe vomiting, diarrhea or high doses of diuretics occur in daily life, doctors in hospitals will check the blood electrolyte test. The blood electrolyte test is a test of the levels of various electrolytes (mainly sodium, potassium, chloride, calcium, magnesium, etc.) in the human blood to assist doctors in diagnosing and treating diseases. These electrolytes are involved in important life activities in the body and change (increase or decrease) when disease states are present, and monitoring can identify and guide treatment. 1. Sodium Increased is commonly seen in anterior pituitary tumors, hyperadrenocorticism, severe dehydration, central uremia, traumatic brain injury, and cerebrovascular accidents. Decrease is common in adrenocortical insufficiency, excessive loss of digestive fluid (such as vomiting, diarrhea), severe pyelonephritis, serious damage to the renal tubules, application of diuretics, large sweating, extensive burns, polyuric phase of uremia, etc. 2, potassium Increased intake is common due to excessive intake, such as too much potassium too quickly, excessive use of potassium-containing drugs. Impaired excretion of potassium is seen in renal failure, hyperalgesia, and long-term use of potassium-protective diuretic drugs. Increased extracellular potassium migration, as seen in large burns, trauma, tissue crush injuries, severe hemolysis, etc. Decreases are common in hyperadrenocorticism, severe vomiting, diarrhea, diuretics and metabolic alkalosis, low potassium diet, etc. 3, calcium Increased commonly in vitamin D excess disease, hyperparathyroidism, multiple bone tumors, etc. 4, magnesium Increase is common in hypothyroidism, renal failure, multiple myeloma, etc. Low common in vomiting, diarrhea, the use of diuretics, chronic renal failure, hyperparathyroidism, long-term use of glucocorticoids, hypercalcemia, etc. There are also some other examples such as iron ions and zinc ions. When performing a blood electrolyte test, the following things should be noted in general: 1. Normally, it is usually necessary to draw blood on an empty stomach. 2. In special cases or emergencies, blood will be drawn for urgent examination at any time to guide treatment.