Currently, approximately 17% of patients with ulcerative colitis and Crohn’s disease experience clinical intolerance to azathioprine, such as severe bone marrow suppression, pancreatitis, liver damage, lymphoma, and even skeletal joint pain, hair loss, and gastrointestinal problems (e.g., nausea, vomiting, discomfort), especially for those with blood neutrophils < 2.0; blood amylase > 2X; or Liver function ALT, ALP, rGT > 2X should be taken more seriously. For these problems, azathioprine should be discontinued immediately: 1. It is recommended that treatment can be switched to 6-mercaptoguanine (6-MP), generally at doses between 0.3 – 1.0 mg/kg, depending on the patient’s condition, which can bring 2/3 of patients intolerant to azathioprine under control. 2. If Crohn’s disease patients remain intolerant to 6-MP, conversion to methotrexate (MTX) therapy is recommended. 3. If there are still patients who are intolerant to the above 2 drugs, consider the use of enteral and parenteral nutrition or biologic therapy, etc.