CA-125 Blood Test (Ovarian Cancer)
Reviewed
This test measures the amount of a protein called CA-125 (cancer antigen 125) in your blood. CA-125 is a tumor marker that can be elevated in ovarian cancer, but also in non-cancerous conditions such as endometriosis, pelvic inflammatory disease, uterine fibroids, liver disease, menstruation, and pregnancy. The test is most commonly used to monitor ovarian cancer treatment and check for recurrence. It is not used for general screening because high levels do not always mean cancer and normal levels do not rule it out.
Preparation and collection
You don't need any special preparations for this test.
Understanding this test
Use the reference interval and units printed by the laboratory that performed the test. A result outside that interval is not a diagnosis by itself, and a result inside it does not rule out every condition. Your symptoms, history, medicines, timing, and related tests can change what the result means.
- High CA-125 levels do not always mean ovarian cancer; they can be caused by non-cancerous conditions such as endometriosis, pelvic inflammatory disease, uterine fibroids, liver disease, menstruation, and pregnancy.
- A normal CA-125 test result does not rule out ovarian cancer, because CA-125 levels may be low in the early stages of cancer, and not everyone with ovarian cancer makes high levels of CA-125.
- Only a biopsy can diagnose ovarian cancer.
What to do next
Talk with your provider if you have questions about your results. Your provider will review your CA-125 test results along with other information about your condition to determine the need for more testing.
Evidence source
U.S. National Library of Medicine: CA-125 Blood Test (Ovarian Cancer)