Elderly people with potassium deficiency, leg weakness and tenderness need to take potassium citrate as prescribed by doctor and find the original disease for treatment, meanwhile, they can eat more food to replenish potassium. 1. Food for potassium: Eat foods rich in potassium, such as bananas, kiwis, oranges and soybeans. 2. Drugs to replenish potassium: If the degree of potassium deficiency is serious, take potassium citrate or intravenous potassium chloride as prescribed by the doctor, which can replenish potassium quickly, but it should be noted that when potassium chloride is fed into the vein, the speed should not be too fast and the concentration should not be too high. 3. Treatment of the original disease: the cause of low potassium needs to be found, such as diarrhea and primary aldosteronism. Diarrhea can discharge a large amount of intestinal fluid, taking away electrolytes from the body; primary aldosteronism causes potassium deficiency because of the increase of urinary potassium, which needs to be treated with spironolactone or surgical treatment. There are many causes of potassium deficiency in the elderly, which should be examined and treated under the guidance of a doctor.