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CA 19-9
Tumor marker of the pancreas and bile ducts, used for monitoring known disease. Benign biliary conditions raise it too.
Other names: Cancer antigen 19-9, carbohydrate antigen 19-9Section: Tumor markers
Updated: August 31, 2026·MedProtect editorial team Reference information — not a diagnosis or a prescription
In shortCA 19-9 is a marker associated mainly with pancreatic and biliary tract cancers. A typical upper limit is 37 U/mL. It is not a screening test: levels rise in pancreatitis, cholecystitis, and any bile-flow blockage. Its main role is monitoring treatment and recurrence.
Reference ranges
Group
Reference range
Typical range — typical range (international reference, not a national standard)
0–37 U/mL
Range from Lab Tests Online (international reference, not a national standard). The report's own interval applies.
Check your value
Enter the number from your lab report — see how it compares with the typical range. Mind the units shown in the chosen row.
A rough comparison with a typical range, not a diagnosis. Reference ranges vary between laboratories — check the range on your own report and let a clinician interpret the result.
What this marker is
CA 19-9 is produced by cells of the pancreatic and biliary ducts. In known pancreatic cancer, serial levels help judge response to therapy and detect recurrence after surgery.
Up to 5–10% of people cannot produce the antigen at all (Lewis blood-group negative), so a normal value never excludes disease.
When it is high
Pancreatic and biliary cancers (known disease)Serial levels track response to treatment and recurrence.
Bile-flow blockageCholestasis of any cause — stones, strictures, cholangitis — can raise the level sharply and reversibly.
Pancreatitis and other benign conditionsInflammation of the pancreas, liver disease, and cystic fibrosis can elevate the marker.
When it is low
Expected findingMost healthy people have low values; Lewis-negative individuals produce none.
What can skew the result
These factors can shift the value without any disease — worth considering before a retest:
Cholestasis and jaundicePancreatitisLewis blood-group status
How to prepare
Blood from a vein; no special preparation.
When a retest makes sense
An elevation during jaundice is usually rechecked after bile flow is restored. In cancer follow-up — on the oncologist's schedule.
Who usually reviews this result
A result outside the reference range is usually reviewed by: a gastroenterologist; an oncologist for known disease. Bring your lab report and any previous results to the appointment.
Names used on lab reports
Your report may use any of these names: CA 19-9Cancer antigen 19-9Carbohydrate antigen 19-9
Units
Measured in: U/mL
Several markers on your report?
See how MedProtect explains results in the app: the whole report, a check of the recognized values, and a clear breakdown.
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