High carcinoembryonic antigen may be caused by tumor factors and non-tumor factors. 1. Tumor factors: high carcinoembryonic antigen is commonly found in malignant tumors, such as pancreatic cancer, breast cancer, gastric cancer, colorectal cancer, lung cancer, etc. These malignant tumors will lead to the increase of synthesis of carcinoembryonic antigen, and the increase of carcinoembryonic antigen will enter into the blood lymphatic circulation, which will lead to the abnormally high carcinoembryonic antigen in the blood serum. 2. Non-tumor factors: cirrhosis, hepatitis, emphysema, diabetes mellitus, etc. can cause high carcinoembryonic antigen, but the carcinoembryonic antigen caused by non-tumor factors won’t be too much higher, and it is suggested that patients should do a reexamination after a period of time, if the result of the reexamination tends to be normal, it indicates that the last high carcinoembryonic antigen may not be related to malignant tumors. If the carcinoembryonic antigen is high, the patient should consult a doctor immediately to identify the cause of the disease and cooperate with the doctor for standardized treatment.