The CA-125 (Cancer Antigen 125) test is a blood test that measures the level of CA-125 protein, primarily used to monitor ovarian cancer treatment and recurrence, and sometimes for high-risk screening, though it’s not for general screening because many non-cancerous conditions (like endometriosis, fibroids, menstruation, pregnancy, PID, liver disease) can also raise levels. Elevated levels don’t automatically mean cancer; they signal the need for further investigation, often with an ultrasound, to check for ovarian issues