In case of potassium deficiency and weakness of legs, oral or intravenous potassium supplementation is required as prescribed by the doctor to quickly restore the blood potassium level, while actively treating the primary disease causing the potassium deficiency and reviewing the blood electrolytes regularly. Patients with potassium deficiency mainly show symptoms such as flaccid paralysis, anorexia, nausea, muscle weakness, vomiting, etc. In severe cases, potassium deficiency may also lead to respiratory muscle paralysis, which has the risk of death. Therefore, in case of potassium deficiency and weakness, one should consult a doctor in a timely manner to clarify the blood potassium level and follow the doctor’s instructions to replenish potassium through oral medication or intravenous potassium supplementation. Usually, the weakness will be relieved when the blood potassium level returns to normal. During potassium supplementation, blood potassium level should be closely monitored to prevent hyperkalemia from occurring. In addition to potassium supplementation, treatment should also be directed to the cause of the disease. Low potassium may be caused by massive vomiting, diarrhea, primary aldosteronism, etc., and the primary disease should be actively treated. Potassium supplementation should be administered in strict compliance with medical advice, and should not be administered blindly, as excessive potassium supplementation also carries health risks.