Blood test
CEA Test
A CEA test measures a protein that can be raised in some cancers, mainly used to monitor bowel cancer rather than to diagnose it.
Quick answer
CEA Test: what it is and what the results mean
CEA (carcinoembryonic antigen) is a protein measured in the blood. It can be produced by certain cancers, particularly bowel (colorectal) cancer, but also rises in some non-cancerous conditions.
- Why it is done: It is mainly used to monitor people already diagnosed with bowel cancer — checking response to treatment and watching for recurrence — rather than to diagnose cancer in the first place.
- Understanding results: A falling level after treatment is reassuring, while a rising level may suggest the cancer is returning and prompt further tests.
What it is
CEA (carcinoembryonic antigen) is a protein measured in the blood. It can be produced by certain cancers, particularly bowel (colorectal) cancer, but also rises in some non-cancerous conditions.
Why it is done
It is mainly used to monitor people already diagnosed with bowel cancer — checking response to treatment and watching for recurrence — rather than to diagnose cancer in the first place.
What to expect
It is an ordinary blood test from a vein in the arm, needing no special preparation. Levels are often tracked over time to look for changes.
Understanding the results
A falling level after treatment is reassuring, while a rising level may suggest the cancer is returning and prompt further tests. Smoking and some benign conditions can also raise CEA, so trends matter more than a single value.
Good to know
Risks and limitations
It is a safe blood test but not reliable for diagnosis or screening, as many cancers do not raise it and benign conditions can. It is most useful for tracking change over time in known cancer.
Education and reference only. This explains the test in general terms and is not medical advice. Always follow the specific instructions from the team arranging your test, and discuss your results with your clinician.
Answers
CEA Test: frequently asked questions
Why is CEA measured over time rather than once?
A single value is less useful than the trend. After cancer treatment, a rising CEA can be an early sign of recurrence, so repeated measurements are compared to look for changes.
Can smoking affect my CEA level?
Yes. Smoking and some non-cancerous conditions can raise CEA modestly, which is one reason the test is interpreted alongside your history and other investigations.
Related tests
Other blood test investigations
Sources
Where this is drawn from
- NHS — Tests and treatments
- NICE — diagnostic guidance
- Association for Laboratory Medicine / relevant professional body
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