The normal value of carcinoembryonic antigen is less than 5.0ng/ml, which is a kind of tumor marker and is useful for determining the presence of cancer, the effect of cancer treatment and whether the cancer is recurrent and metastatic. Usually, when the normal value of carcinoembryonic antigen is higher than normal, it indicates a certain risk, i.e. carcinoembryonic antigen is considered dangerous when it is higher than 5.0ng/ml. The specificity of carcinoembryonic antigen in diagnosing tumors is not high. It is found in many malignant tumors such as gastric cancer, colorectal cancer, breast cancer, pancreatic cancer, liver cancer, medullary thyroid cancer, lung cancer, ovarian cancer, etc. If carcinoembryonic antigen is greater than 5.0ng/ml, it needs to be noticed; if it exceeds 7.5ng/ml, patients should be carefully asked whether they have any uncomfortable symptoms, and if necessary, CT or ultrasound should be done to determine whether malignant tumor occurs; if it exceeds 10.0ng/ml, it indicates that the risk of tumor is relatively high, and relevant examination is feasible to avoid misdiagnosis and leakage. However, it is inaccurate to judge whether a person is suffering from tumor only by the amount of high carcinoembryonic antigen, because carcinoembryonic antigen > 5.0ng/ml does not necessarily mean suffering from cancer. Some people with smoking, alcoholism, inflammation, cardiovascular disease during pregnancy, diabetes, colitis, pancreatitis, intestinal diverticulitis, rectal polyps, liver cirrhosis, hepatitis, lung disease, etc. may also have elevated carcinoembryonic antigen. Therefore, when elevated carcinoembryonic antigen is found and accompanied by physical discomfort, one should immediately consult a doctor and get a clear diagnosis through relevant examinations to avoid delaying the disease.