Cimetidine is available in injectable and oral formulations with varying side effects. Side effects such as diarrhea, bloating, dry mouth, and mild elevation of serum aminotransferase are more common with the injectable formulation of cimetidine, and adverse reactions such as severe hepatitis, hepatic necrosis, and hepatic steatosis are occasionally seen. There is a certain inhibitory effect on the bone marrow, and temporary moderate leukopenia or granulocytopenia may occur in a few patients. Higher doses of the drug may cause gynecomastia, female breast spillage, decreased libido and impotence. Cimetidine oral formulation may occasionally cause sore throat and fever, unexplained bleeding or petechiae, and unusual lethargy and weakness. Mental disorders may also occur, mostly in elderly or seriously ill patients. Gynecomastia, lactation, loss of libido, diarrhea, dizziness, headache, rash, and hair loss may occur with prolonged use or increased dosage. It is prohibited for women and nursing mothers. It is prohibited for those who are allergic to this product. Cimetidine is a prescription drug, it is recommended to follow the doctor’s instructions to take.