There is no such thing as a maximum side effect of cimetidine, and the magnitude of side effects is related to an individual’s body type and so on. Some of the more common adverse effects of cimetidine are diarrhea, headache, fatigue, dizziness, and rash. A few patients also experience mental disorders, sore and hot throat, bleeding or ecchymosis, fatigue, and granulocytopenia. Gynecomastia, lactation, decreased libido, muscle cramps, myalgia, and alopecia occur with prolonged heavy use of the drug. Cimetidine is a histamine H2 receptor impedant, with the effect of inhibiting the secretion of gastric acid, mainly used in the treatment of duodenal ulcer, gastric ulcer, reflux esophagitis, stress ulcers, Dreweiler-Ayer’s syndrome and other diseases. Use of the drug should be noted that patients who are allergic to cimetidine are prohibited, pregnant and lactating women are prohibited, and the use of this drug is not recommended for children under 16 years of age. If you need to use cimetidine, it is recommended to consult a professional doctor, follow the doctor’s instructions for standardized treatment, not blindly self-medication.