The information on this page was reviewed and approved by
Maurie Markman, MD, President, Medicine & Science at CTCA.

This page was updated on September 21, 2021.

CEA testing

A CEA test measures the level of carcinoembryonic antigen (CEA) in your blood or other body fluid, as an indicator of whether cancer is growing and spreading or diminishing with treatment. You may be tested before treatment to set a baseline level, then again during and after treatment.

What is CEA?

While in the uterus, an unborn baby produces CEA, but healthy adults produce little or none of this protein. Smokers may have elevated levels, as well as people with the following noncancerous conditions:

  • Emphysema
  • Cirrhosis
  • Benign breast disease
  • Inflammation of the gallbladder (cholecystitis)
  • Inflammation of the pancreas (pancreatitis)
  • Peptic ulcer
  • Ulcerative colitis
  • Rectal polyps

High levels correspond to the presence of colorectal cancer, as well as cancers of the pancreas, liver, stomach, ovaries, thyroid, lungs and breast.

Carcinoma refers to cancers that arise from epithelial tissue, which lines and covers organs and includes your skin. Carcinomas make up the bulk of cancer cases—80 to 90 percent, according to the National Cancer Institute. Adenocarcinomas are carcinomas that begin in a gland or organ, often in a mucus membrane. Any cancer classified as an adenocarcinoma may generate CEA.

Because many types of cancer and several noncancerous conditions may cause high CEA levels, doctors don’t use CEA tests to diagnose a specific form of cancer or determine whether you have cancer. Rather, they’re used to monitor progress of certain treatments.

CEA is one of several substances called tumor markers that cancer cells release into the bloodstream.

Others tests for cancer include:

  • CA-125, an indicator of cancer of the ovaries, fallopian tubes or peritoneum (a layer of tissue enclosing your abdominal organs)
  • PSA, or prostate-specific antigen
  • HCG, or human chorionic gonadotropin, a sign of cancer of the ovaries, testicles or the spaces between the lungs or behind the intestines
  • CA 19-9, associated with cancer of the bile ducts or pancreas

Getting tested

Most commonly, CEA tests involve taking a blood sample, a simple procedure where blood is withdrawn from one of your veins via a needle into a syringe or test tube. Less often, fluid may be collected from other parts of your body, depending upon the type of cancer and where a tumor may be located. Fluid may be extracted from along the peritoneum, the pleural space surrounding your lungs, or next to your spinal cord.

A blood test requires no preparation on your part. You may experience slight discomfort from the needle and soreness and bruising afterward. Before both the spinal and abdominal procedures, you may be asked to go to the bathroom. The cerebrospinal fluid test may cause soreness and pain in the back, where the needle was inserted, and occasionally a headache afterward. Although generally considered safe, both the abdominal and pleural fluid tests carry a small risk of tissue damage and infection—as well as possible blood loss for the pleural test.

Test results

Before undergoing cancer treatment, you may have your CEA levels tested. Typically, a low level indicates a small tumor that hasn’t spread elsewhere in the body. A high level may correspond to a larger tumor or cancer that has spread—or metastasized—to one or more locations away from the original site. Results may be compared with levels taken during and after therapy as a way to better understand how the cancer has responded to treatment.

Test results that drop during treatment indicate therapy helped, and levels that remain high show treatment probably hasn’t curbed the cancer. If your CEA levels drop during treatment, but rise afterward, it may signal a recurrence.

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