Drugs have influence on carcinoembryonic antigen, such as antibiotic drugs and drugs affecting the gastrointestinal tract, etc. Carcinoembryonic antigen can be regarded as a kind of tumor marker, its specificity and sensitivity are not high, and it can only play an auxiliary role in diagnosis. 1. Antibiotics: the effect of antibiotics on carcinoembryonic antigen will mainly lead to the disorders of normal flora in the body, which has a certain effect on the body. Moreover, carcinoembryonic antigen is a kind of broad-spectrum tumor marker, which can reflect the existence of many kinds of tumors. 2. Drugs affecting the gastrointestinal tract: such as colchicine tablets, roxithromycin tablets, etc. These drugs can promote the activity of the large intestine, thus causing diarrhea and fluctuating the carcinoembryonic antigen, which fluctuates with a very small amplitude, and after stopping the drugs, it can make the value of carcinoembryonic antigen return to normal. Drugs have influence on carcinoembryonic antigen, so it is suggested that patients should follow the doctor’s instructions when taking drugs. Usually, patients should take more rest, avoid overwork, avoid drinking alcohol to avoid affecting the gastrointestinal tract, if carcinoembryonic antigen is elevated and suspected to be related to the drugs, it is recommended to repeat the examination after stopping the drugs.