• Also Known As:
  • Carbohydrate Antigen 19-9
  • Cancer Antigen-GI
  • CA-GI
  • CA 19-9
Medically Reviewed by Expert Board

This page was fact checked by our expert Medical Review Board for accuracy and objectivity. Read more about our editorial policy and review process.

This article was last modified on
Learn more about...
  • 1
    Order Your Test

    Online or over the phone

  • 2
    Find a Lab Near You

    Over 3,500 locations to choose from

  • 3
    Get Your Results
    Sent Directly to You

At a Glance

Why Get Tested?

Primarily to monitor response to pancreatic cancer treatment and to watch for recurrence; sometimes to aid in the diagnosis of pancreatic cancer

When To Get Tested?

During and/or following pancreatic cancer treatment

Sample Required?

A blood sample drawn from a vein; sometimes a healthcare practitioner will collect samples of other body fluids.

Test Preparation Needed?


What is being tested?

Cancer antigen 19-9 (CA 19-9) is a protein that exists on the surface of certain cancer cells. CA 19-9 does not cause cancer; rather, it is shed by the tumor cells and can be detected by laboratory tests in blood and sometimes other body fluids. This test measures the level of CA19-9.

Since CA 19-9 can be measured in blood, it is useful as a tumor marker to follow the course of the cancer. CA 19-9 is elevated in about 70% to 95% of people with advanced pancreatic cancer. (Read more in the “How is the test used?” section under Common Questions and in the Pancreatic Cancer article.)

However, CA 19-9 may also be elevated in other cancers, conditions, and diseases such as: gallbladder and bile duct cancers (cholangiocarcinoma), colorectal cancer, gastric cancers, ovarian cancer, lung cancer, liver cancer, bile duct obstruction (e.g., gallstones), pancreatitis, cystic fibrosis, thyroid disease, and liver disease. Small amounts of CA 19-9 are present in the blood of healthy people. Since CA 19-9 is not specific for pancreatic cancer, it cannot be used by itself for screening or diagnosis.

The European Group on Tumor Markers (EGTM) and National Comprehensive Cancer Network (NCCN) recommend use of CA 19-9 as a tumor marker for pancreatic cancer in addition to other tests and examinations to diagnose and monitor the disease.


Common Questions

How is the test used?

The CA 19-9 test may be used, along with other tests such as carcinoembryonic antigen (CEA), bilirubin, and/or a liver panel, to help evaluate and monitor a person who has been diagnosed with pancreatic cancer and is undergoing treatment.

CA 19-9 is used as a tumor marker:

  • To monitor response to pancreatic cancer treatment and/or cancer progression
  • To watch for pancreatic cancer recurrence
  • Sometimes to aid in the diagnosis of pancreatic cancer

CA 19-9 can only be used as a tumor marker if the cancer is producing elevated amounts of it. Since CA 19-9 is elevated in about 65% of those with bile duct cancer (cholangiocarcinoma), it may be ordered to help evaluate and monitor people with this type of cancer.

The CA 19-9 test is not sensitive or specific enough to use as a screening test for cancer. It is not currently useful for detection or diagnosis by itself because non-cancerous conditions can cause elevated CA 19-9 levels. Researchers continue to investigate markers to be used alone or in combination with CA 19-9 that may be more useful for screening for and detecting pancreatic cancer in the early stages, when it is most treatable.

When is it ordered?

CA 19-9 may be ordered when you have been diagnosed with pancreatic cancer and/or has signs and symptoms that may indicate pancreatic cancer. Early signs and symptoms may be subtle and nonspecific. Examples include:

  • Abdominal and/or back pain
  • Nausea
  • Loss of appetite
  • Unexplained weight loss
  • Jaundice

In later stages, there may be chronic pain, nausea, vomiting, malabsorption, and, in some rare instances, problems with blood glucose control.

If CA 19-9 is initially elevated in pancreatic cancer, then a series of CA 19-9 tests may be ordered during cancer treatment to monitor response and on a regular basis following treatment to help detect recurrence.

CA 19-9 may sometimes be ordered when a healthcare practitioner suspects bile duct cancer in a person with a bile duct obstruction. Non-cancerous causes of bile duct obstruction can cause very high CA 19-9 levels, which fall when the blockage is cleared. In these cases, it is a good idea to wait at least a week or two after the blockage is relieved (by placing a tube, or stent, in the bile ducts) to re-check CA 19-9 levels.

What does the test result mean?

Low amounts of CA 19-9 can be detected in healthy people, and many conditions that affect the liver or pancreas can cause temporary elevations.

Moderate to high levels may be seen in people with pancreatic cancer, other cancers, and in several other diseases and conditions. The highest levels of CA 19-9 are seen in cancer of the exocrine pancreas. This cancer arises in the tissues that produce food-digesting enzymes and in the ducts that carry those enzymes into the small intestine. About 95% of pancreatic cancers are of this type.

Levels of CA 19-9 that are initially high and then fall over time may indicate that the treatment is working and/or that the cancer was removed successfully during surgery. Levels that remain high or rise over time may indicate that treatment is not working and/or that the cancer is recurring.

Is it important to use the same lab each time I have a CA 19-9 test done?

Yes. Laboratories may use different methods to test for CA 19-9, so results can vary from lab to lab. If you are having a series of CA 19-9 tests done, it is advised that you have the tests done by the same method, typically by the same laboratory, so that the results can be compared and interpreted correctly. You may wish to discuss this issue with your healthcare practitioner.

Why is my healthcare practitioner not screening me for CA 19-9?

CA 19-9 is not sensitive or specific enough to be recommended as a screen for people who do not have symptoms. There are too many false positives and false negatives associated with it. Researchers are looking for other markers that may help detect pancreatic cancer at an earlier stage and that may be more suitable for screening.

What other procedures will my healthcare practitioner likely order along with CA 19-9?

Your healthcare practitioner may order a CT scan (computed tomography), an ultrasound, an MRI scan to look at the pancreatic and bile ducts, and/or an ERCP (endoscopic retrograde cholangiopancreatography, a procedure in which a small lighted tube is passed through the mouth and stomach into the duodenum and then into the bile and pancreatic ducts). For more details on this, see RadiologyInfo.org. Your healthcare practitioner may also order a biopsy to look for cancer cells under the microscope.

What are the main risk factors for pancreatic cancer?

Healthcare practitioners still do not know what causes most cases of pancreatic cancer. Identified risk factors include tobacco use (smoking and smokeless products), age (most are over 50 years old), sex (men are slightly more likely to have it than women), family history, diabetes, chronic pancreatitis, and workplace exposure to certain chemicals, such those used in the dry cleaning and metal working businesses.

Is there anything else I should know?

Unfortunately, early pancreatic cancer gives few warning signs. By the time a person has symptoms and significantly elevated levels of CA 19-9, pancreatic cancer is usually at an advanced stage.

CA 19-9 is a protein on the surface of cells. It is derived from a blood group antigen called Lewis antigen that is similar to the ABO antigens that are used in blood typing for transfusions. About 5% to 7% of people are Lewis antigen-negative (about 30% in people of African ancestry) and do not produce CA 19-9. The CA 19-9 test is not useful for monitoring people who are Lewis antigen-negative.

You may be able to find your test results on your laboratory’s website or patient portal. However, you are currently at Lab Tests Online. You may have been directed here by your lab’s website in order to provide you with background information about the test(s) you had performed. You will need to return to your lab’s website or portal, or contact your healthcare practitioner in order to obtain your test results.

Lab Tests Online is an award-winning patient education website offering information on laboratory tests. The content on the site, which has been reviewed by laboratory scientists and other medical professionals, provides general explanations of what results might mean for each test listed on the site, such as what a high or low value might suggest to your healthcare practitioner about your health or medical condition.

The reference ranges for your tests can be found on your laboratory report. They are typically found to the right of your results.

If you do not have your lab report, consult your healthcare provider or the laboratory that performed the test(s) to obtain the reference range.

Laboratory test results are not meaningful by themselves. Their meaning comes from comparison to reference ranges. Reference ranges are the values expected for a healthy person. They are sometimes called “normal” values. By comparing your test results with reference values, you and your healthcare provider can see if any of your test results fall outside the range of expected values. Values that are outside expected ranges can provide clues to help identify possible conditions or diseases.

While accuracy of laboratory testing has significantly evolved over the past few decades, some lab-to-lab variability can occur due to differences in testing equipment, chemical reagents, and techniques. This is a reason why so few reference ranges are provided on this site. It is important to know that you must use the range supplied by the laboratory that performed your test to evaluate whether your results are “within normal limits.”

For more information, please read the article Reference Ranges and What They Mean.

View Sources

Sources Used in Current Review

2019 review performed by Mustafa A. Barbhuiya, PhD, MLS (ASCP) MB (ASCPi).

Duffy MJ, Sturgeon C, Lamerz R, Haglund C, Holubec VL, Klapdor R, Nicolini A, Topolcan O, Heinemann V. Tumor markers in pancreatic cancer: a European Group on Tumor Markers (EGTM) status report. Ann Oncol. 2010; 21(3): 441-7. Available online at https://www.ncbi.nlm.nih.gov/pubmed/19690057. Accessed July 2019.

NCCN Clinical Practice Guidelines. National Comprehensive Cancer Network. Fort Washington, PA. Available online at https://www.nccn.org/professionals/physician_gls/default.aspx. Accessed July 2019.

Duffy MJ, Lamerz R, Haglund C, Nicolini A, Kalousová M, Holubec L, Sturgeon C. Tumor markers in colorectal cancer, gastric cancer and gastrointestinal stromal cancers: European group on tumor markers 2014 guidelines update. Int J Cancer. 2014; 134(11): 2513-22. Available online at https://www.ncbi.nlm.nih.gov/pubmed/23852704. Accessed July 2019.

Smith RA, Cokkinides V, Brooks D, Saslow D, Brawley OW. Cancer screening in the United States, 2010: a review of current American Cancer Society guidelines and issues in cancer screening. CA Cancer J Clin. 2010; 60(2): 99-119. Available online at https://www.ncbi.nlm.nih.gov/pubmed/20228384. Accessed July 2019.

Sources Used in Previous Reviews

Thomas, Clayton L., Editor (1997). Taber’s Cyclopedic Medical Dictionary. F.A. Davis Company, Philadelphia, PA [18th Edition].

Pagana, Kathleen D. & Pagana, Timothy J. (2001). Mosby’s Diagnostic and Laboratory Test Reference 5th Edition: Mosby, Inc., Saint Louis, MO.

ACS. All About Pancreatic Cancer, Pancreatic Cancer Detailed Guide. American Cancer Society.

ASCO (1996 May 17, adopted, revision every 3 years). CA 19-9 as a Marker for Colon Cancer. American Society for Clinical Oncologists, Clinical Practice Guidelines for the Use of Tumor Markers in Breast and Colorectal Cancer [On-line guidelines]. Available online at http://www.asco.org/prof/pp/html/guide/tumor/m_tumor6.htm.

NCI (2002, February 8, posted). What you Need to Know about Cancer of the Pancreas. National Cancer Institute, cancer.gov [On-line information]. Available online through http://www.cancer.gov.

Reid, C. (1996 October). Probing the Pancreas. U.S. Food and Drug Administration [On-line article]. Available online at http://vm.cfsan.fda.gov/~dms/fdpancre.html.

Mayer, R. (1999 – 2002 copyright). Pancreatic Cancer. The National Pancreas Foundation [On-line article]. Available online at http://www.pancreasfoundation.org/pancreaticcancerarticle.html.

Check, W. (1998 July) Reaching agreement on tumor markers. CAP Today, In the News [On-line journal]. Available online at http://www.cap.org/captoday/archive/1998/julycover.html.

NCI (1998 April 27). Tumor markers. National Cancer Institute, Cancer Facts [On-line information]. Available online at http://cis.nci.nih.gov/fact/5_18.htm.

ACS (2000 July 19). Tumor Markers. American Cancer Society, Prevention and Early Detection [On-line information]. Available online through http://www.cancer.org.

Pagana, K. D. & Pagana, T. J. (© 2007). Mosby’s Diagnostic and Laboratory Test Reference 8th Edition: Mosby, Inc., Saint Louis, MO. Pp 216-217.

Clarke, W. and Dufour, D. R., Editors (© 2006). Contemporary Practice in Clinical Chemistry: AACC Press, Washington, DC. Pg 246.

(Revised 2008 December 08). Tumor Markers. American Cancer Society [On-line information]. Available online at http://www.cancer.org/docroot/PED/content/PED_2_3X_Tumor_Markers.asp?sitearea=PED. Accessed August 2009.

(Updated 2009 May) Tumor Markers. ARUP Consult [On-line information]. Available online at http://www.arupconsult.com/resources/print/TumorMarkers.pdf. Accessed August 2009.

Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. Burtis CA, Ashwood ER and Bruns DE, eds. 4th ed. St. Louis, Missouri: Elsevier Saunders; 2006 Pg 773.

(Revised 2012 October 18). American Cancer Society. Tumor Markers [On-line information]. PDF available for download at http://www.cancer.org/acs/groups/cid/documents/webcontent/003189-pdf.pdf. Accessed October 2012.

Thaker, N. et. al. (Updated 2012 May 23). CA 19-9. Medscape Reference [On-line information]. Available online at http://emedicine.medscape.com/article/2087513-overview#showall. Accessed October 2012.

(© 1995-2012). Carbohydrate Antigen 19-9 (CA 19-9), Serum. Mayo Clinic Mayo Medical Laboratories [On-line information]. Available online at http://www.mayomedicallaboratories.com/test-catalog/Overview/9288. Accessed October 2012.

(© 2012). Diagnosis CA 19-9. Pancreatic Cancer Action Network [On-line information]. Available online at http://www.pancan.org/section_facing_pancreatic_cancer/learn_about_pan_cancer/diagnosis/CA19_9.php. Accessed October 2012.

Pagana, K. D. & Pagana, T. J. (© 2011). Mosby’s Diagnostic and Laboratory Test Reference 10th Edition: Mosby, Inc., Saint Louis, MO. Pp 208-209.

Clarke, W., Editor (© 2011). Contemporary Practice in Clinical Chemistry 2nd Edition: AACC Press, Washington, DC. Pg 500.

Thaker NG. CA 19-9. (5 September 2014 updated.) Available online at http://emedicine.medscape.com/article/2087513-overview. Accessed July 1, 2016.

American Cancer Society (5 April 2016 revised). Tests for Pancreatic Cancer. Available online at http://www.cancer.org/cancer/pancreaticcancer/detailedguide/pancreatic-cancer-diagnosis. Accessed July 1, 2016.

American Cancer Society (20 January 2016 revised). How is Bile Duct Cancer Diagnosed? Available online at http://www.cancer.org/cancer/bileductcancer/detailedguide/bile-duct-cancer-diagnosis. Accessed July 7, 2016.

National Cancer Institute (4 November 2015 reviewed). Tumor Markers. Available online at http://www.cancer.gov/about-cancer/diagnosis-staging/diagnosis/tumor-markers-fact-sheet. Accessed June 28, 2016.

Penn Medicine Oncolink® (28 April 2016 updated). Patient Guide to Tumor Markers. Available online at http://www.oncolink.org/treatment/article.cfm?id=296. Accessed June 28, 2016.

De Paula JMP, Toranzo EM, Borge LG, Hidalgo SF. Small-cell Lung Cancer and Elevated CA 19.9 Tumor Marker Levels. Archivos de Bronconeumología. 2012;48(10):382–387. PDF available online at http://www.archbronconeumol.org/en/small-cell-lung-cancer-elevated-ca/articulo/S1579212912001450/. Accessed July 1, 2016.

Canadian Cancer Society. Carbohydrate antigen 19-9 (CA19-9). Available online at http://www.cancer.ca/en/cancer-information/diagnosis-and-treatment/tests-and-procedures/carbohydrate-antigen-19-9-ca-19-9/?region=on. Accessed July 3, 2016.

Pagana, Kathleen D., Pagana, Timothy J., and Pagana, Theresa N. (© 2015). Mosby’s Diagnostic and Laboratory Test Reference. 12th Edition: Mosby, Inc., Saint Louis, MO. Pp 197-198.

Chustecka, Zosia. (Jan. 21, 2014.) New Test for Pancreatic Cancer Based on MicroRNAs in Blood. Medscape. Available online at http://www.medscape.com/viewarticle/819481. Accessed July 2016.