Methotrexate is used to treat rheumatoid arthritis, psoriatic arthritis, ankylosing spondylitis, and many other autoimmune diseases, using doses typically 7.5 mg to 20 mg per week. For rheumatologists and patients, in order to avoid or reduce the side effects of methotrexate, the following points should be noted when prescribing or taking methotrexate: 1. Check blood and urine routine and liver and kidney function every 2 weeks for the first 3 months after starting, and every 1-3 months thereafter; 2. Use with caution or do not use for a long time in patients with a history of hepatitis and avoid alcohol; 3. Patients with megaloblastic anemia, oral ulcer, mild liver damage or severe peripheral neuritis may add folic acid 5 mg 3 times a day; 4. Female patients should stop using methotrexate for 6 months to 1 year before pregnancy to prevent the occurrence of malformations. It has been reported that the incidence of methotrexate is 30%; 5. Severe diarrhea and ulcerative stomatitis should be considered for discontinuation to prevent hemorrhagic enterocolitis and fatal intestinal perforation; 6. If there is also ascites or pleural fluid, the dose of methotrexate should not be too high.