The CEA blood test measures carcinoembryonic antigen (CEA) levels in the blood, a protein that may be elevated in certain cancers, such as colorectal and thyroid cancer, and in conditions like gastritis and diabetes. This test is commonly used as a tumor marker to help track changes in the body.
The CEA blood test is mainly used to monitor how colorectal and thyroid cancers respond to treatments like surgery, chemotherapy, and radiation therapy. It can also help detect whether cancer has returned after treatment or if it has spread to other parts of the body.
Abnormal CEA blood test results may occur with symptoms like weight loss or diarrhea, but high levels do not always mean cancer. Elevated CEA can also be linked to conditions like smoking, lung disease, or inflammatory bowel disease, and further testing is usually needed to confirm the cause.
What the test is used for
The CEA blood test may be ordered to:
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Monitor the response to treatment with surgery, chemotherapy, and/or radiation therapy in cases of colorectal or thyroid cancer
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Confirm whether colorectal or thyroid cancer has been completely removed after surgery
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Identify whether colorectal or thyroid cancer has returned after surgical treatment.
According to the National Cancer Institute, follow-up after colorectal cancer treatment may include imaging tests and CEA blood testing to monitor for recurrence.
The CEA blood test may also sometimes be used to help evaluate fluid buildup in the abdomen, known as ascites, or in the lungs, called pleural effusion, which may be a sign of tumors or metastases.
Understanding your results
CEA levels in the blood considered normal are:
- In smokers: up to 5.0 ng/mL
- In non-smokers: up to 3.0 ng/mL
The reference range for the CEA blood test may vary by laboratory, and smoking status should always be considered.
CEA levels can be elevated in people without cancer. However, levels higher than 20 ng/mL are generally linked to a higher likelihood of cancer, particularly more advanced disease, and usually require additional testing.
Causes of high CEA levels
In addition to colon or thyroid cancer, CEA blood test results may be elevated in cases of:
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Smoking
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Chronic obstructive pulmonary disease (COPD)
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Diabetes
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Lung infections
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Inflammatory bowel disease
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Other tumors, such as pancreatic, breast, or lung cancer
Therefore, a high CEA level in the blood does not always indicate cancer, and doctors usually order further tests to confirm or rule out a diagnosis.