Test guide
CA-125 Blood Test (Ovarian Cancer)
This test measures the amount of a protein called CA-125 (cancer antigen 125) in a sample of your blood. CA-125 is a type of tumor marker. Tumor markers are substances that are often made by cancer cells or by normal cells in response to cancer.
What it is for
Measuring certain tumor markers often help health care providers treat cancer. So, because high levels of CA-125 can be a sign of ovarian cancer, a CA-125 blood test can help your provider: Your provider cannot use a CA-125 to screen for ovarian cancer if you aren't at high risk. That's because other conditions that aren't cancer can also cause high CA-125 levels. These include: Source: MedlinePlus, National Library of Medicine. Medical test information is public domain. Source identity and definition checked automatically on 2026-10-18. No individual clinical interpretation or human reviewer is asserted.
Limitations
Reference intervals and interpretation depend on the laboratory, specimen, method and clinical context. This source definition is educational information; it does not establish a diagnosis, product approval or suitability for an individual.
Also known as
- cancer antigen 125, glycoprotein antigen, ovarian cancer antigen, CA-125 tumor marker
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