What Is the CEA Test?

Medically Reviewed by Jennifer Robinson, MD on August 17, 2022
3 min read

Doctors don’t always see obvious signs of cancer growth after a diagnosis. They need to hunt for clues. One way they can do that is with a carcinoembryonic antigen test. It measures a protein called CEA in the blood.

People with some types of cancers have higher than normal levels of this substance. This test helps your doctor find out if yours has grown and whether your treatment has worked.

CEA is a type of protein in the body. Babies in the womb have high levels of it. After birth, levels drop way down. Healthy adults have a very low level, but some types of cancer can cause it to rise.

Your doctor can use CEA as a “marker” to learn more about your cancer.

The test can often help predict whether the cancer is growing or spreading to other parts of your body. It can also help tell how well your treatment has worked and predict your outlook.

Your doctor might give you a CEA test if you're diagnosed with one of these cancers:

Doctors don't use the CEA test to make a first-time diagnosis of cancer. This test isn't an accurate way to screen for it because many other diseases can cause the levels of this protein to rise. And some people with cancer don't have high CEA levels.

This test can help your doctor plan and monitor your treatment once you know you have cancer. You might get the test:

  • After your diagnosis to help your doctor find the right treatment
  • During treatment to see how well chemotherapy, radiation, surgery, or other therapies have worked
  • After treatment to help find out whether the cancer has come back

You don't need to do anything ahead of time. Tell your doctor if you:

Also let your doctor know about any drugs you take. Include vitamins, supplements, and medicines you bought without a prescription.

The test takes a sample of your blood. It can be done in the doctor's office.

The doctor will place a needle into a vein in your arm to draw out the blood. You might feel a slight pinch or sting when the needle goes in.

Sometimes doctors will test CEA levels in another bodily fluid, such as:

  • Cerebrospinal (from the spine)
  • Peritoneal (from the abdomen)
  • Pleural (from the area next to the lungs)

You may need to go to a hospital for these tests.

With the needle stick, you might have:

  • Bleeding
  • Infection
  • Bruising
  • Dizziness
  • Soreness where the needle was placed in your arm

Your blood sample will be sent to a lab. Special machines will check it for cancer.

A normal result is typically less than 2.5 nanograms per milliliter. Results might vary between labs. A higher-than-normal CEA level that increases over time might signal that your cancer has grown or has come back after treatment.

But high levels of CEA do not always mean you have cancer. These other conditions can also increase levels:

You might also have higher than normal levels if you are pregnant or you smoke.

Your doctor will explain your test results to you. If you have a cancer that has grown, they will go over your treatment options.