What does it measure?
Carcinoembryonic antigen is a protein-related marker that is usually present at low levels in adult blood. It may be useful in following colorectal cancer and some other cancers when the marker was informative at diagnosis. It is not a substitute for recommended colorectal screening.
Before the test
- Sample
- A blood sample from a vein.
- Smoking
- Tell the clinician whether you smoke, because it can raise CEA.
What can the result mean?
A higher CEA may prompt further assessment, but can also occur with smoking and noncancerous conditions. A normal value does not rule out cancer because not all tumors produce it. Trends may support a treatment assessment but cannot determine the result alone. [1]
When is it useful, and how is it read?
Read CEA mainly in the follow-up of a cancer for which the marker is useful, alongside the pretreatment value, symptoms, and imaging. Smoking and noncancerous liver or inflammatory conditions can complicate the trend. [1] [2]
What can affect it?
Smoking status, inflammation, liver conditions, treatment timing, and the laboratory method affect interpretation. Comparing measurements made with a consistent method helps make changes easier to interpret. [1]
Myth: «CEA can replace recommended bowel-cancer screening»
CEA is not a reliable screening test for people without a known cancer. A normal result cannot replace screening appropriate to your age, history, and local care plan. [1]
Questions you might have
Can CEA screen me for cancer?
No. Its main use is following selected known cancers; healthy people and noncancerous conditions can also have raised values. [1]
Why is my result before treatment useful?
It shows whether CEA was informative for your cancer and gives later results a baseline for comparison. [1]
What comes next?
If CEA is part of an established follow-up plan, review it alongside symptoms, examination, and imaging. If it was ordered for a general checkup, ask what clinical question it answers; it should not be used alone to look for cancer in healthy people. [1]
Was CEA useful at diagnosis in my case, and what evidence would confirm the meaning of a change?
The reference interval and units on your report are part of understanding your result. Understand units, reference intervals, and treatment targets.
Sources & references
Medical references & original research
- MedlinePlus — CEA test
- ASCO — Biomarkers for Systemic Therapy in Metastatic Breast Cancer: Guideline Update (2022)
Books we consulted
References that informed our explanations of the test and its context.
- Pagana KD, Pagana TJ, Pagana TN. Mosby’s Diagnostic and Laboratory Test Reference. 14th ed. Elsevier; 2019.
Practical-section sources accessed: .
For general health education. Interpreting your result and deciding on tests or treatment requires your health context and a qualified clinician.
