Carcinoembryonic Antigen (CEA) Test
The CEA test measures serum carcinoembryonic antigen, a glycoprotein re-expressed and shed by many epithelial cancers. It is principally used to monitor colorectal cancer after treatment, detect recurrence, and assess response to therapy, with baseline and serial trends more informative than isolated values.
1
Biomarkers
Blood (serum)
Sample
1–3 business days
Turnaround
No
Fasting
What is the CEA test?
The Carcinoembryonic Antigen (CEA) Test measures serum concentration of a glycoprotein that is normally suppressed after birth but re-expressed and shed by many epithelial cancers. It is ordered primarily to monitor patients with colorectal cancer after curative surgery or chemotherapy, where serial values detect recurrence months ahead of symptoms or imaging, and to assess response to therapy in metastatic disease. CEA also contributes to the initial staging and prognostic assessment of gastrointestinal, lung, and breast cancers, though it is neither sensitive nor specific enough to diagnose cancer or to screen asymptomatic populations. Practitioners interpret CEA in the context of the patient's smoking status, inflammatory and hepatic comorbidities, and treatment history, recognising that benign elevation is common and that the trend over serial measurements is far more informative than an isolated value.
What does the CEA test measure?
Carcinoembryonic antigen is a glycoprotein normally expressed during foetal development in the gastrointestinal tract and suppressed after birth. Low concentrations circulate in healthy adults, with modest physiological elevation in smokers. CEA belongs to the immunoglobulin superfamily and functions in cell adhesion; its re-expression in malignant epithelial cells reflects dedifferentiation. The molecule is shed into blood and other body fluids, where it can be measured by immunoassay. Its plasma half-life is approximately three to seven days, meaning that levels decline predictably after successful tumour resection and rise again with recurrence or progression.
CEA is principally used in the monitoring of colorectal cancer after treatment, where rising levels indicate recurrence or metastatic progression before imaging becomes positive. It is also elevated in other gastrointestinal malignancies, lung and breast cancers, and in benign conditions including inflammatory bowel disease, liver disease, and smoking. Because of poor specificity and sensitivity, CEA is not recommended as a screening or sole diagnostic test for cancer; instead it serves as an adjunct to imaging and histology in staging, prognosis, and post-treatment surveillance. The baseline pre-treatment value and the trend over time carry more weight than any single result.
Why is the CEA test ordered?
- Post-operative surveillance of colorectal cancer, with serial CEA every three to six months for the first two to three years and less frequently thereafter, according to guideline recommendations
- Baseline pre-treatment measurement in newly diagnosed colorectal, gastric, pancreatic, lung, or breast cancer to inform prognosis and establish an individual reference for follow-up
- Monitoring response to chemotherapy or targeted therapy in metastatic colorectal or other CEA-secreting cancers, where declining levels suggest treatment efficacy
- Investigation of suspected recurrence when a previously low or undetectable CEA begins to rise, prompting imaging and possible salvage therapy
- Adjunct to imaging in the evaluation of indeterminate lesions or equivocal findings in patients with a known CEA-secreting tumour
- Prognostic stratification at diagnosis, where higher pre-treatment CEA correlates with more advanced stage and poorer outcomes in colorectal cancer
- Assessment of completeness of resection, where failure of CEA to normalise post-operatively suggests residual disease
Sample collection and turnaround
Sample type
Blood (serum)
Fasting required
No
Collection method
Venipuncture at patient service centre
Turnaround
1–3 business days
Collection notes
Phlebotomy at the processing laboratory's draw site (Quest or Access Medical Laboratories, depending on routing); no special preparation required. Note the performing laboratory for serial comparability, as assay calibration differs between platforms.
Specimen requirements
Minimum 0.5 mL serum (gel separator acceptable). CEA is stable refrigerated for several days and frozen for months. Avoid haemolysis, which may interfere with some immunoassays.
What can affect CEA results?
Tobacco use raises baseline CEA, with smokers commonly reaching 5 ng/mL or higher without malignancy; use smoking-adjusted reference limits and interpret trends rather than absolute values.
Inflammatory bowel disease, pancreatitis, peptic ulcer, diverticulitis, cirrhosis, and hepatitis can all raise CEA modestly, limiting specificity and necessitating clinical correlation.
Lung, breast, gastric, pancreatic, and ovarian cancers may elevate CEA, so an abnormal result in a patient without known colorectal cancer prompts broader investigation rather than assuming the source.
Different immunoassay platforms yield results that are not directly interchangeable; serial monitoring should use the same laboratory and method to ensure comparability.
Severe renal dysfunction can modestly raise CEA through reduced clearance, though the effect is usually small; correlation with creatinine is prudent in this setting.
Surgery, chemotherapy, or radiation may transiently alter CEA — allow several weeks post-operatively for decay to nadir, and interpret short-term fluctuations during chemotherapy cautiously.
What do CEA results mean?
Elevated
Malignant causes: colorectal, gastric, pancreatic, lung (especially adenocarcinoma), breast, ovarian, and medullary thyroid cancers. Benign causes: smoking, inflammatory bowel disease, pancreatitis, hepatitis, cirrhosis, chronic obstructive pulmonary disease, and benign gastrointestinal conditions. A single elevated CEA is non-specific; the pattern, magnitude (markedly elevated values more often malignant), and trend over time, combined with imaging and histology, guide management.
Normal
A normal CEA does not exclude cancer — many early-stage and even some advanced colorectal cancers do not secrete CEA, and other tumour markers or imaging may be required. Normal post-treatment levels are reassuring but surveillance continues because not all recurrences are CEA-positive.
Reduced
CEA does not fall below a physiological floor, so 'low' values have no clinical significance. A declining CEA after treatment is favourable and reflects tumour response or clearance.
Note: CEA is a monitoring and prognostic tool, not a diagnostic or screening test. The baseline pre-treatment value, the nadir after therapy, and the kinetics of change matter more than any threshold. Serial results must be compared using the same assay platform and laboratory. Smoking history, inflammatory conditions, and liver disease all influence interpretation, and guideline-based surveillance protocols should be followed rather than ordering CEA in isolation.
Frequently asked questions
CEA is most commonly elevated in colorectal cancer and is the standard marker for post-treatment surveillance. It is also raised in gastric, pancreatic, lung, and breast cancers, but it is neither sensitive nor specific enough to diagnose cancer and must be interpreted with imaging and histology.
How to access the CEA test
The CEA reference page is free and open to all practitioners. Create a free practitioner account to see pricing, save tests to your list, and generate requisition forms. Verification takes 1–2 business days.
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Published: October 7, 2026
Last reviewed: October 7, 2026
- Locker GY, et al. ASCO 2006 update of recommendations for the use of tumor markers in gastrointestinal cancer. J Clin Oncol. (2006)
- Duffy MJ, et al. Tumour markers in colorectal cancer: European Group on Tumour Markers (EGTM) guidelines for clinical use. Eur J Cancer. (2007)
- National Comprehensive Cancer Network. NCCN Clinical Practice Guidelines in Oncology: Colon Cancer. (2025)
- Sturgeon CM, et al. National Academy of Clinical Biochemistry laboratory medicine practice guidelines for use of tumor markers in testicular, prostate, colorectal, breast, and ovarian cancers. Clin Chem. (2008)
- Goldstein MJ, Mitchell EP. Carcinoembryonic antigen in the staging and follow-up of patients with colorectal cancer. Cancer Invest. (2005)
This content is for licensed healthcare practitioners only and does not constitute medical advice. Clinical decisions should be based on the full clinical picture and not on any single test result.
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