Furosemide should not be taken when it expires. Taking expired furosemide may cause toxic reactions or side effects, the most common side effects are causing hypokalemia, hypochlorhydria, and hyponatremia. Expired furosemide is also prone to allergic reactions, patients may develop urticaria, interstitial nephritis, and prone to toxic reactions, commonly bone marrow suppression, granulocytopenia, aplastic anemia, liver function impairment, and thrombocytopenic purpura. The efficacy of expired furosemide will be reduced or even ineffective, which is harmful to the treatment instead of working.