What does CA-125 mean on a blood test?
CA-125 is a protein sometimes measured in blood that can be higher with ovarian and some other cancers. It is often used to follow a known cancer over time. Many non-cancer conditions can also raise it, so it is not used alone.
Also written as
- CA125
- cancer antigen 125
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How to read tumor markers results
Tumor markers are substances measured in blood that can run higher when certain cancers are present. They are mainly useful for watching a trend over time — for example, before and after treatment — rather than for diagnosing or ruling out cancer on their own. Levels can rise or fall for reasons that have nothing to do with cancer, and some people with cancer never have a raised marker at all, so a single number can mislead. Your team looks at the direction of change across several tests, together with scans and how you are feeling.
Questions to ask your care team
- What is the trend in this marker across my recent tests?
- Could anything besides cancer be affecting this number?
- How will you use this marker to follow my care over time?
- What change in this level would prompt a next step?
Related tumor markers terms
- Tumor markerA tumor marker is a substance measured in blood that can be higher with some cancers.
- PSAPSA (prostate-specific antigen) is a protein measured in blood, mainly to check the prostate.
- CEACEA (carcinoembryonic antigen) is a blood marker often tracked in colon and some other cancers.
- CA 19-9CA 19-9 is a blood marker linked with pancreatic and some digestive cancers.
- CA 15-3CA 15-3 (and the related CA 27-29) is a blood marker sometimes used to follow breast cancer over time.
- AFPAFP (alpha-fetoprotein) is a blood marker that can be higher with certain liver and testicular cancers.
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