There is no specific level of CEA that indicates cancer. CEA is a protein that is sometimes produced by cancer cells, but it can also be produced by healthy cells in very low levels. Elevated CEA levels can be caused by various types of cancer and several noncancerous conditions. Therefore, CEA tests are not an accurate way to detect a specific form of cancer or determine whether a patient has cancer. In general, a CEA level of more than 2.9 ng/mL is considered abnormal but doesn’t necessarily mean that cancer is present. False-positive results are reported with concentrations as high as 35 ng/mL. Healthcare providers use CEA tests to monitor the progress of certain cancer treatments and to help predict the likelihood of recovery and/or the chance that cancer will come back after treatment.