The most serious complication of oliguria in renal failure is hyperkalemia, which is toxic to the heart and can cause various arrhythmias such as ventricular fibrillation and cardiac arrest when it reaches above 6.0-7.0 mmol/L. Severe arrhythmias may directly lead to the death of the patient and should be treated with hemodialysis at the hospital as soon as possible. Patients with oliguria need to pay attention to their diet, such as oranges, bananas and other foods with high potassium content should be eaten as little as possible, while using less potassium-protecting diuretics, spironolactone potassium-protecting diuretics are more likely to cause an increase in blood potassium. After going to the hospital, hemodialysis can be performed, along with infusion therapy, using glucose, insulin, calcium gluconate, and sodium bicarbonate to lower the blood potassium, so that the patient’s blood potassium to normal. Most importantly, patients should have their blood potassium levels reviewed regularly to prevent elevated blood potassium.