After patients take too much metronidazole, certain adverse reactions may occur, digestive tract reactions are most common, including nausea, vomiting, loss of appetite, abdominal cramps, usually these reactions do not affect the treatment. Neurologic symptoms include headache, vertigo, occasional sensory abnormalities, numbness of the limbs, ataxia, polyneuritis, and so on. After high doses of oral metronidazole, patients may lead to physical convulsions, and in a few cases, allergic reactions may occur, such as urticaria, flushing, and itching, and some have urinary symptoms such as cystitis and dysuria. Some patients have a metallic taste in the mouth, and some blood tests may reveal leukopenia, etc. These adverse reactions are reversible and may recover on their own after stopping the drug.