The main side effects of metronidazole tablets are: i. Gastrointestinal symptoms, such as nausea, vomiting, diarrhea, discomfort in the upper and middle abdomen, abdominal cramps, constipation, etc. ii. Significant metallic odor in the mouth, thick tongue, tongue inflammation, and gastritis. III. Hematologic system reversible granulocytosis and erythrocytopenia. IV. Central nervous system epilepsy, peripheral neuropathy, mental confusion, easy excitement, depression, weakness and insomnia. V. Allergy may present with urticaria, erythematous rash, nasal congestion, dry vulva or fever. Sixth, the urinary system will have difficulty urinating, cystitis, polyuria, urinary incontinence, etc. These are the side effects of metronidazole tablets.