Blood test
CA-125 Test
A CA-125 test measures a protein in the blood that can be raised in ovarian cancer and some other conditions.
Quick answer
CA-125 Test: what it is and what the results mean
CA-125 (cancer antigen 125) is a protein measured in the blood. Levels can rise with ovarian cancer, but also with many non-cancerous conditions, so it is a marker rather than a definite cancer test.
- Why it is done: It is used to help investigate symptoms that could suggest ovarian cancer (such as persistent bloating, tummy pain or feeling full quickly), to monitor known ovarian cancer, and sometimes alongside an ultrasound scan.
- Understanding results: A raised CA-125 may prompt further tests such as an ultrasound and specialist referral, but many benign conditions (like endometriosis, fibroids, menstruation and infections) also raise it.
What it is
CA-125 (cancer antigen 125) is a protein measured in the blood. Levels can rise with ovarian cancer, but also with many non-cancerous conditions, so it is a marker rather than a definite cancer test.
Why it is done
It is used to help investigate symptoms that could suggest ovarian cancer (such as persistent bloating, tummy pain or feeling full quickly), to monitor known ovarian cancer, and sometimes alongside an ultrasound scan.
What to expect
It is a standard blood test from a vein in the arm, needing no special preparation. Results usually come back within a few days.
Understanding the results
A raised CA-125 may prompt further tests such as an ultrasound and specialist referral, but many benign conditions (like endometriosis, fibroids, menstruation and infections) also raise it. A normal level does not fully exclude cancer.
Good to know
Risks and limitations
It is a safe blood test but not a screening test for the general population, because it is neither specific nor sensitive enough. It is always interpreted alongside symptoms and imaging.
Education and reference only. This explains the test in general terms and is not medical advice. Always follow the specific instructions from the team arranging your test, and discuss your results with your clinician.
Answers
CA-125 Test: frequently asked questions
Does a raised CA-125 mean I have ovarian cancer?
No. Many non-cancerous conditions raise CA-125, including endometriosis, fibroids, pelvic infection and even menstruation. A raised level prompts further tests rather than confirming cancer.
Can CA-125 be used to screen for ovarian cancer?
It is not recommended as a screening test for people without symptoms, because it misses some cancers and is raised by many harmless conditions. It is used to investigate symptoms and monitor known cancer.
Related tests
Other blood test investigations
Sources
Where this is drawn from
- NHS — Tests and treatments
- NICE — diagnostic guidance
- Association for Laboratory Medicine / relevant professional body
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