What is a CEA test?

A carcinoembryonic antigen (CEA) test measures a specific blood glycoprotein called CEA. It means a protein with a lot of sugars added to it by normal or cancerous cells. Scientists first discovered CEA in 1968 when they isolated extracts of liver metastasized by colorectal cancer and also from normal fetal digestive tract. Everyone is born with high levels of this protein. CEA decreases as you get older, but some conditions, including certain types of cancer, can increase your blood CEA levels.

CEA is sometimes called a tumor marker or tumor antigen. Tumor markers are substances that some cancer cells make and shed into bodily fluids at times. Healthy cells also may make tumor markers in very low levels. Many healthy people have “normal” level of tumor makers, which is called normal range, reference range or reference interval on lab reports.

What kind of cancer is CEA test used for?

CEA doesn’t necessarily tell you whether you have cancer and providers don’t use it to screen for cancer. It instead should be used in people who’ve been previously diagnosed with certain types of cancer, most commonly colorectal cancer.

Providers also use CEA along with other tests as they diagnose, treat and follow-up on a range of cancers, including bladder, breast, lung, ovarian and thyroid cancer. It’s typically used for monitoring response to treatment including relapses and to look for possible recurrences. But this test isn’t used in isolation. Your provider will combine it with physical examination and imaging as needed.

When is a CEA test needed?

Healthcare providers don’t use CEA tests to diagnose cancer. But the tests can show important information if you already know you have cancer. Your healthcare provider may use a CEA test to:

• Check if cancer has grown or spread (metastasized) to other parts of your body.
• Evaluate how well cancer treatment is working.
• You might have the test:
• Immediately after diagnosis to help guide your treatment plan (baseline testing).
• During cancer treatment, to see how well treatments like chemotherapy, immunotherapy, or radiation therapy are working.
• After completion of cancer treatment to check if cancer has returned (recurrence).
• After you have a diagnosis, and before you have treatment and/or surgery. Your provider then tests it every one to three months during active treatment. But a rise in CEA level four to six weeks after initiation of therapy doesn’t necessarily mean treatment failure, relapse or recurrence.
• In remission, you may need regular CEA tests to watch for possible recurrences. Your physician may decide on the frequency of testing.

How does a CEA test work?

A CEA test is usually a blood test. During a blood test, your healthcare provider takes a small blood sample from one of your veins. Specialists in a laboratory analyze the blood to check for CEA.

Less commonly, your provider may test fluid from your:

• Abdominal wall (peritoneal fluid).
• Chest (pleural fluid).
• Spinal cord (cerebrospinal fluid or CSF).

In these cases, your provider takes a small fluid sample using a needle or syringe. They insert the needle or syringe into your chest or lower back.

How do I prepare for a CEA test?

Your healthcare provider will tell you how to prepare for a CEA test. You may temporarily stop certain medicines or supplements that increase bleeding, like aspirin.

What can I expect during a CEA test?

During a CEA blood test, your healthcare provider:

1. Inserts a small needle into one of your veins, usually in your arm.
2. Attaches a vial or test tube to the needle.
3. Collects a small blood sample.

If your healthcare provider needs to take samples of other body fluids, they:

1. Inject your lower back or chest with numbing medicine (local anesthesia).
2. Insert a needle or syringe into the area.
3. Use an X-ray image to guide the needle to the correct position.
4. Collect a sample of CSF, pleural fluid or peritoneal fluid.

A CEA blood test usually takes less than five minutes. CEA tests of other body fluids usually take 30 minutes or less. You can return home the same day.

What are the risks of a CEA test?

CEA tests are generally safe. Chest fluid tests have a small risk of:

• Blood loss.
• Infection.
• Lung damage.

Most people don’t experience complications of a CEA test. Your healthcare provider will help you understand the risks of the test beforehand.

What are the side effects of a CEA test?

If you have a blood test, you may have mild pain or bruising where your provider inserted the needle.

If your provider took samples of CSF or abdominal fluid, side effects may include:

• Dizziness.
• Headaches.
• Lightheadedness.

What do the results of a CEA test mean?

Your healthcare provider uses CEA test results to learn more about cancer:

• Low CEA levels could mean a tumor is small and hasn’t spread to other parts of your body. But certain types of cancer don’t shed as much CEA, especially those limited to certain areas such as your brain, blood CEA tests may show low CEA levels. This is where your physician considers imaging techniques such as MRI.
• High CEA levels could mean a tumor is large or has spread to other parts of your body. But CEA can’t be used for tumor staging or determining if your cancer has metastasized.

Your healthcare provider may also test your CEA levels throughout cancer treatment. If your CEA levels significantly decrease throughout treatment, it often means your treatment is working. Providers generally conduct a physical exam and imaging to determine this.

What is a normal CEA level?

CEA is typically reported in nanograms per milliliter (ng/mL). The reference range is 0-2.9 ng/mL of blood. Generally, healthcare providers consider typical CEA levels to be between 0 and 2.9 ng/mL. Research indicates that false-positive results are reported with concentrations as high as 35 ng/mL.

Different labs may have slightly different references ranges and clinicians may consider higher thresholds depending on the individual circumstances.

What levels of CEA indicate cancer?

There’s no magic number or threshold for a CEA test that points to cancer. Healthcare providers don’t use the CEA test to screen for or diagnose 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.

Can CEA levels be high without cancer?

Yes. High CEA levels don’t necessarily mean you have cancer. For example, smoking cigarettes may increase your CEA levels. The following non-cancer conditions can result in increased CEA levels:

• Gastritis (inflammation of your stomach) and stomach ulcers.
• Chronic Obstructive Pulmonary Disease (COPD).
• Liver diseases like cirrhosis, fatty liver or gallstones.
• Diverticulitis.
• Diabetes.
• Any autoimmune or inflammatory disease.
• Inflammatory bowel diseases (Crohn’s disease and ulcerative colitis).
• Hemorrhoids.
• Pneumonias (including COVID-19 pneumonia).

Certain people exposed to therapeutics that are fully or partially derived from animals like monoclonal antibodies also have elevated CEA levels.

A note from Cleveland Clinic

A CEA test measures your levels of CEA. CEA is a blood glycoprotein. Certain types of cancer can increase your CEA levels, but you can have high CEA without having cancer. Healthcare providers don’t use these tests to diagnose cancer. But if you already have a cancer diagnosis, your provider may use the test to guide or monitor your treatment.