Folic acid can prevent anemia caused by long-term use of methotrexate. Because methotrexate is a dihydrofolate reductase inhibitor, so that the body can not convert dihydrofolate into physiologically active tetrahydrofolate, long-term use of the plasma concentration of folic acid will be reduced, resulting in anemia. Methotrexate should be supplemented with folic acid, and blood and liver functions should be checked regularly. Methotrexate may cause anemia, nausea, stomatitis, diarrhea, alopecia, rash, bone marrow suppression, hearing impairment, interstitial lung lesions, miscarriage, teratology and other adverse reactions. Note that severe hepatic and renal impairment, alcoholism or chronic alcoholism, severe or chronic infections, gastrointestinal ulcers patients are prohibited. Special Population: contraindicated in pregnant and lactating women. Folic acid is essential for the growth and reproduction of cells in the body, and its deficiency will lead to the blockage of red blood cell production and anemia. Folic acid may produce an allergic reaction after the use of medication, long-term use of the drug will be nausea, abdominal distension and other gastrointestinal reactions. Note that this product is contraindicated in people who are allergic to it. Pernicious anemia, and megaloblastic anemia where the cause cannot be determined, require combination therapy with vitamin B12. The use of methotrexate by patients must be carried out under the supervision of a specialized doctor and strictly comply with medical recommendations.