Skip to content

Carbohydrate Antigen 19-9 (CA 19-9)

Published: July 27, 2026Updated: August 25, 2026

CA 19-9 is a tumor marker that measures the levels of a specific protein in the blood, often elevated in patients with pancreatic, gastrointestinal, and biliary tract cancers.

Quick summary

CA 19-9 is a blood marker used to monitor pancreatic and gastrointestinal cancers.

Medically reviewed by WellAlly Editorial TeamLast reviewed August 25, 2026Editorial policy

Key facts at a glance

Units
U/mL
Clinical utility
monitoring
Result kind
quantitative
FDA-cleared
Roche CA 19-9, Abbott CA 19-9, Siemens CA 19-9, Fujirebio CA 19-9
interpretation: {"text":"0–37 U/mL: Normal range, low likelihood of cancer.","label":"Normal"}; {"text":">37 U/mL: Possible indication of cancer, further investigation required.","label":"Elevated"}

CA 19-9, or Carbohydrate Antigen 19-9, is a protein that is often found at elevated levels in the blood of patients with certain types of cancer, particularly pancreatic cancer. It is used as a tool for monitoring the progression of the disease and the effectiveness of treatment.

While CA 19-9 is not recommended for use in cancer screening due to its lack of specificity, it is valuable in tracking the response to therapy and detecting recurrence in patients who have already been diagnosed with cancer.

Normal levels of CA 19-9 are typically below 37 U/mL. Elevated levels may indicate the presence of cancer, but can also be caused by other conditions such as gallstones, pancreatitis, and liver disease.

Frequently asked questions

What cancers is CA 19-9 associated with?
CA 19-9 is most commonly associated with pancreatic cancer, but can also be elevated in gastrointestinal and biliary tract cancers.
Can CA 19-9 be used for cancer screening?
No, CA 19-9 is not recommended for cancer screening due to its lack of specificity and potential for false positives.
  1. 1
    National Cancer Institute - Tumor MarkersSource
  2. 2
    American Cancer Society - CA 19-9Source

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 25, 2026. · Read our editorial policy