The use of azathioprine generally requires monitoring of blood levels as prescribed by the physician. Azathioprine is one of the most commonly used immunosuppressants in clinical practice. Due to individual differences in the sensitivity and tolerance of patients to immunosuppressants, when taking the same dose of immunosuppressants, the blood concentration of different patients is not exactly the same; so clinically need to monitor the patient’s blood concentration to adjust the dosage of immunosuppressants, which is conducive to the rationalization of the development of the therapeutic program. The common adverse reactions of azathioprine are myelosuppression, liver damage, muscle and joint pain, nausea and vomiting, etc.; and usually occurs in the first 3 months of taking the drug, monitoring blood concentration is conducive to assessing the patient’s tolerance of azathioprine, and when the above adverse reactions occur, the doctor will assess whether to adjust the dosage of the drug. It is important to note that azathioprine is contraindicated in people who are allergic to the components of the drug, people with severe infections, people with tuberculosis, people with impaired hepatic or renal function, people with a history of pancreatitis, and people who have been vaccinated with a live vaccine within the past four weeks, and that pregnant women and breastfeeding mothers must be evaluated by a doctor specializing in this area. If adverse reactions such as abdominal pain, rash, cough, fever, severe diarrhea, etc. occur during the administration of the drug, the drug should be stopped immediately and prompt medical attention should be sought. Do not take medication on your own.