What Is Carcinoembryonic Antigen (CEA) Negative?

Carcinoembryonic antigen (CEA) is a tumor marker produced by tumors within the body. It is primarily detected via blood testing and is clinically used for screening and assessing malignant tumors; however, it is not the primary basis for diagnosing malignancy. A negative CEA result—defined as a CEA protein level ≤5 ng/mL—is considered within the normal reference range. Nevertheless, this does not definitively rule out the presence of a tumor; clinical evaluation must therefore integrate other relevant signs and symptoms.