A CEA (carcinoembryonic antigen) blood test measures the level of CEA in the blood. CEA is a protein that is normally found in the tissue of a developing baby in the womb, and the blood level of this protein disappears or becomes very low after birth. In adults, an abnormal level of CEA may be a sign of cancer. However, a higher than normal CEA level alone cannot diagnose a new cancer, and further testing is needed. The CEA test is often used in people who have been diagnosed with cancers that often increase CEA levels. It is also used to monitor the progress of certain treatments.

The normal range for CEA in the blood is 0 to 2.5 ng/mL (0 to 2.5 µg/L) . In smokers, slightly higher values may be considered normal (0 to 5 ng/mL, or 0 to 5 µg/L) . However, different labs may have slightly different reference ranges. A high CEA level in a person recently treated for certain cancers may mean the cancer has returned. Cancers that may cause high levels of CEA include breast cancer, cancers of the reproductive and urinary tracts, colon cancer, lung cancer, pancreatic cancer, and thyroid cancer. An increased CEA level may also be due to liver and gallbladder problems, heavy smoking, or inflammatory bowel diseases.

The CEA test is usually a blood test, and during the test, a healthcare provider takes a small blood sample from one of the patients veins. The test may also use fluid from the abdominal wall, chest, or other parts of the body, depending on the type of cancer and where a tumor may be located. No fasting is required for the test, but smoking may increase the CEA level, so patients who smoke may be advised to avoid smoking for a short time before the test.