Carcinoembryonic antigen has a normal value of <5.0ng/ml. If carcinoembryonic antigen is found to reach more than 100ng/ml, it needs to be alerted, and the situation is relatively dangerous if it is due to cancer. If it is caused by diabetes, diverticulitis of the intestine and other benign lesions, it is relatively not dangerous. Carcinoembryonic antigen was initially extracted as a tumor-associated antigen in diseases such as colon cancer, but with clinical practice, in addition to malignant tumors of the gastrointestinal tract that can lead to elevated carcinoembryonic antigen, it can also be caused by benign lesions. Therefore it is not possible to generalize whether carcinoembryonic antigen reaching more than 100ng/ml is dangerous. If carcinoembryonic antigen reaches 100ng/ml or more due to malignant tumors such as colorectal cancer, pancreatic cancer, gastric cancer, etc., the situation is relatively dangerous, and timely diagnosis and treatment are needed, otherwise it will be life-threatening. However, if the carcinoembryonic antigen is mildly elevated due to benign lesions such as diabetes mellitus, intestinal diverticulitis, pancreatitis, etc., the situation is relatively not dangerous, but it needs active treatment. If carcinoembryonic antigen is found to reach more than 100ng/ml, one should keep a good mood, avoid too much tension, and go to regular hospitals for further examination and clear diagnosis.