Under normal circumstances, smoking does not cause elevated carcinoembryonic antigen. Smoking is very harmful to human health, mainly due to the fact that tobacco contains a lot of carcinogenic substances, which is one of the high-risk factors leading to cancer, but generally speaking, it does not lead to the elevation of carcinoembryonic antigen (CEA). Carcinoembryonic antigen is a kind of tumor indicator, and elevated carcinoembryonic antigen is mostly seen in colorectal cancer, gastric cancer, pancreatic cancer, hepatocellular carcinoma, lung cancer, breast cancer, medullary thyroid cancer, etc. In addition, mild elevation of CEA can be seen in some benign gastrointestinal diseases, such as intestinal obstruction, biliary obstruction, pancreatitis, cirrhosis of the liver, colorectal polyp, ulcerative colitis, smokers, and the elderly, and 25% of this kind of patients have a temporary elevation of serum CEA. temporarily elevated. If carcinoembryonic antigen is elevated, patients are advised to go to regular hospitals for further examination to exclude the possibility of the presence of gastrointestinal malignant tumors, hepatobiliary malignant tumors, and lung malignant tumors.