Isoniazid is a major and important drug in anti-tuberculosis treatment, with good efficacy, but adverse reactions can occur, in the following aspects: 1. Liver function damage, patients can suffer from loss of appetite and abnormal liver function in the course of taking the drug, especially the incidence is higher in patients who are malnourished, older and have liver disease themselves; 2. Peripheral neuritis, manifested as numbness and foreign body sensation at the ends of the limbs, especially Chronic renal insufficiency, diabetes mellitus or high-dose isoniazid users have a higher incidence; 3. Central nervous system damage, manifested as insomnia, patients with pre-existing epilepsy or psychosis can induce seizures; 4. Allergic reactions, manifested as rash, itching, or even fever; 5. Inhibition of the hematological system, manifested as leukopenia and thrombocytopenia; 6. Other rare adverse reactions, such as endocrine disorders. Pay attention to close observation and regular review when using isoniazid, so as to detect adverse reactions early and make timely treatment.