The normal value of carcinoembryonic antigen will not exceed 6.0 ng/ml. carcinoembryonic antigen is a tumor marker used to detect the presence or absence of tumor in the body and to determine the efficacy of tumor treatment. it is widely used to determine the efficacy of intestinal cancer, breast cancer and lung cancer and to evaluate the healing process. Carcinoembryonic antigen is not a specific marker for malignant tumors, and it is only an auxiliary diagnostic role in diagnosis and treatment, and has a suggestive role in the diagnosis of early gastrointestinal tumors. Generally, elevated carcinoembryonic antigen is routinely needed to exclude the possibility of GI inflammation or tumor diseases. Since patients with early stage of tumor will not show the phenomenon of increased carcinoembryonic antigen, so do not judge the tumor by the value of carcinoembryonic antigen. If the carcinoembryonic antigen is high, further examination is needed.