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CEA (Carcinoembryonic Antigen)

A protein that some cancers release, mainly colorectal. It is used to follow people with cancer, not to screen healthy people.

AI-verified against cited sources. Awaiting expert reviewAlso called CEALOINC 2039-6

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What it is

CEA stands for carcinoembryonic antigen. It is a protein made before birth, and adults normally have very little of it. Colorectal cancer and some other cancers release more CEA into the blood. Smoking, liver disease and long-term inflammation can also raise it. The number alone cannot tell which cause is behind a high level.

Why it matters

CEA is used mainly to follow people who have already been diagnosed with colorectal cancer. A falling level can be a sign that treatment is working, and a level that keeps rising may lead your clinician to look for the cancer coming back. It is not used to screen healthy people or to diagnose cancer, because many people with early cancer have a normal CEA and many raised results come from other causes. Your clinician will read the number together with your history, symptoms, scans and earlier CEA results.

If it’s high

A level above your lab's range does not mean you have cancer. Smoking and many non-cancer conditions raise CEA, and levels creep up with age. If you have had colorectal cancer, your clinician will compare the result with your earlier ones and look at the trend. If you have no cancer history, your clinician will usually repeat the test and ask about symptoms and smoking before deciding on anything else. Published reviews link levels above about 10 ng/mL, or levels that keep rising, more often with cancer, but even then other causes are possible.

Common causes

  • Smoking (healthy smokers often run higher than non-smokers)
  • Older age, and slightly higher levels in men
  • Liver conditions such as cirrhosis, gallstones or fatty liver disease, because the liver clears CEA
  • Lung disease such as COPD
  • Bowel and stomach inflammation, such as gastritis, stomach ulcers, diverticulitis, Crohn's disease or pancreatitis
  • Diabetes
  • Colorectal cancer, and some other cancers such as lung, pancreatic, breast and ovarian cancer

What can help

  • Ask your clinician whether to repeat the test, since one result is rarely enough to act on
  • Tell your clinician if you smoke, and about any liver, lung or bowel conditions you have
  • If you have had colorectal cancer, ask how this number compares with your earlier ones, and use the same lab each time
  • If the level stays high, ask which other tests or exams would help in your case

Usual ranges

What labs print as the reference range, by who was tested. Ranges differ a little between labs, so the range on your own report is the one your result is judged against.

For adults: 0–3.8 ng/mL. Source: ARUP Laboratories, UW Medicine Laboratory Medicine & Pathology, University of Iowa Hospitals & Clinics Pathology Handbook, Michigan Medicine Laboratories (MLabs), Scandinavian Journal of Clinical and Laboratory Investigation, Medical Science Monitor, Journal of Medical Systems.

What can affect your result

  • Smoking: raises CEA, mainly in men in one screening study
  • Age: levels rise slowly with age
  • Sex: levels run a little higher in men
  • Liver and bile duct problems, which slow the clearing of CEA
  • Assay method: results from different methods are not interchangeable
  • Biotin supplements and antibodies against mouse proteins (HAMA), which can distort some immunoassays
  • Chemotherapy: in about 10–15% of people with advanced colorectal cancer CEA rises briefly after treatment starts, which does not always mean the cancer is growing
  • Smoking raises CEA. MedlinePlus says people who smoke may be asked to stop for a while before the test, so tell your clinician if you smoke.
  • High-dose biotin (more than about 5 mg) can falsely lower results on some immunoassays. The University of Iowa Hospitals asks that no sample be drawn until 12 hours after the last dose.
  • Antibodies against mouse proteins (HAMA), which can follow treatment or imaging with mouse-based antibody products, can make results falsely high or low.
  • Results from different assay methods are not interchangeable (ARUP, UW Medicine). Follow-up results are easiest to compare when they come from the same lab and method.
  • On the electrochemiluminescence method used at the University of Iowa Hospitals, hemolysis, lipemia and jaundice do not interfere up to high levels.

CEA is cleared by the liver. A published review says it takes about 35 days (five half-lives) to fall to a new steady level after colorectal cancer surgery in people with normal liver function.

When to talk to a clinician

Talk with your clinician soon if your CEA keeps rising on repeat tests, or if it is above your lab's range and you have new symptoms such as blood in your stool, a lasting change in bowel habits, unexplained weight loss, belly pain that does not go away, or a cough that will not clear. If you are being followed after colorectal cancer, tell your care team about any rise, even a small one, since the trend over time matters. Published reviews link levels above about 10 ng/mL more often with cancer, so ask about next steps if your result is that high.

Questions you could ask

  • Why was a CEA test ordered for me?
  • Should I use the same lab each time so results can be compared?
  • How often should this be checked in my situation?
  • Could smoking or another condition I have explain this result?
  • Should we repeat the test, and when?
  • How does this number compare with my earlier CEA results?

Questions people ask

Does a high CEA mean I have cancer?

No. Many things raise CEA, and most are not cancer. Smoking, liver disease, lung disease such as COPD, and bowel inflammation are common reasons. CEA is not used to screen for or diagnose cancer. If your level is high, your clinician will usually repeat the test and look at the trend, your symptoms and other tests.

Why is the upper limit different for smokers?

Smoking raises CEA, so healthy smokers often run higher than non-smokers. Some labs print a separate limit for smokers. UW Medicine, for example, says healthy smokers are generally below 5.5 ng/mL on its Roche method, while its limit for everyone is 3.7 ng/mL. Use the range printed on your own report.

How often is CEA checked after colorectal cancer treatment?

It depends on the stage and on your care team's plan. ASCO advises a visit, exam and CEA every 3 to 6 months for 5 years. The European Group on Tumor Markers suggests every 2 to 3 months for at least 3 years for stage II or III disease. A single rise is usually confirmed with a second sample before more tests are ordered.

Show the science and sources

Units

  • 1 ng/mL = 1 ng/mL
  • 1 ng/mL = 1 µg/L

Is a change real?

CEA naturally varies about 6.8% from test to test in the same healthy person. Between two results from the same lab, a rise of 23% or more, or a fall of 19% or more, is unlikely to be day-to-day noise or lab variation (95% reference change value). Source: Critical review and meta-analysis of biological variation estimates for tumor markers (Marques-Garcia F et al., EFLM WG-BV).

For clinicians and researchers

CEA is a fetal glycoprotein present at low levels in adults. At least 90% is removed on first pass through the liver (Hall 2019), which is why liver or bile duct disease can raise serum levels, and the same review states that 95% of the fall to a new steady level after resection takes five half-lives, or about 35 days. Assays are immunoassays; ARUP uses the Roche electrochemiluminescence method and UW Medicine has used Beckman and Roche methods. Both labs state that results from different methods cannot be used interchangeably. High-dose biotin and heterophile or HAMA antibodies can distort results (University of Iowa Hospitals). ARUP states that a CEA value, regardless of level, should not be read as evidence for or against malignancy and is not recommended for screening. Cut-offs are debated: a Cochrane review of 52 studies, as summarized by Hall 2019, found sensitivity and specificity for recurrence of 82% and 80% at 2.5 ng/mL, 71% and 88% at 5 ng/mL, and 68% and 97% at 10 ng/mL, and suggested 10 ng/mL as the level to trigger further work-up. After curative colon surgery, the accuracy of a 5 ng/mL threshold at 6 months was 89.1% when the pre-operative CEA was normal and 58.4% when it was raised. ASCO (2006) recommends a pre-operative CEA when it would help staging or surgical planning, CEA every 3 months for stage II and III disease for at least 3 years in people who could have surgery or chemotherapy for metastases, and CEA as the marker of choice for monitoring response of metastatic disease to systemic therapy. ASCO's 2013 endorsement of the Cancer Care Ontario guideline advises history, exam and CEA every 3 to 6 months for 5 years. The European Group on Tumor Markers (2014) advises a baseline and then every 2 to 3 months for at least 3 years in stage II and III disease, confirmation of any rise with a second sample, and use of the same assay throughout. It also notes transient CEA rises in 10–15% of people with advanced colorectal cancer given chemotherapy. CEA is also raised in non-gastrointestinal cancers (lung, breast, ovarian, pancreatic and medullary thyroid cancers) and in benign disease, so it has low specificity.

LOINC 2039-6 (primary), 83085-1. Specimen: serum-or-plasma.

Sources

  1. Carcinoembryonic Antigen (test 0080080), ARUP Laboratories
  2. Carcinoembryonic Antigen (Roche) (lab code CEARD), UW Medicine Laboratory Medicine & Pathology
  3. Carcinoembryonic Antigen (Beckman) (lab code CEA), UW Medicine Laboratory Medicine & Pathology
  4. Carcinoembryonic Antigen (CEA), University of Iowa Hospitals & Clinics Pathology Handbook
  5. Carcinoembryonic Antigen (test CEA), Michigan Medicine Laboratories (MLabs)
  6. CEA Test, MedlinePlus (National Library of Medicine)
  7. Tumor Markers in Common Use, National Cancer Institute
  8. A review of the role of carcinoembryonic antigen in clinical practice, Annals of Coloproctology (2019)
  9. Tumor markers in colorectal cancer, gastric cancer and gastrointestinal stromal cancers: European group on tumor markers 2014 guidelines update, International Journal of Cancer (2014)
  10. ASCO 2006 update of recommendations for the use of tumor markers in gastrointestinal cancer, Journal of Clinical Oncology (2006)
  11. Follow-up care, surveillance protocol, and secondary prevention measures for survivors of colorectal cancer: American Society of Clinical Oncology clinical practice guideline endorsement, Journal of Clinical Oncology (2013)
  12. Reference intervals for carcinoembryonic antigen (CEA), CA125, MUC1, Alfa-foeto-protein (AFP), neuron-specific enolase (NSE) and CA19.9 from the NORIP study, Scandinavian Journal of Clinical and Laboratory Investigation (2008)
  13. Reference Intervals of Alpha-Fetoprotein and Carcinoembryonic Antigen in the Apparently Healthy Population, Medical Science Monitor (2016)
  14. Influence of smoking on serum carcinoembryonic antigen levels in subjects who underwent multiphasic health testing and services, Journal of Medical Systems (1998)

AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.

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