CA 125 is a protein that is measured in a blood test. It is primarily used as a tumor marker for ovarian cancer. The CA 125 test is often performed in individuals who have symptoms suggestive of ovarian cancer, such as pelvic pain, bloating, or abnormal vaginal bleeding. It may also be used to monitor the response to treatment or detect the recurrence of ovarian cancer. However, it is important to note that CA 125 can also be elevated in non-cancerous conditions, such as endometriosis, pelvic inflammatory disease, or even during menstruation. Therefore, the CA 125 test is not a definitive diagnostic tool for ovarian cancer, but it can provide valuable information when used in conjunction with other diagnostic tests and clinical evaluation. A healthcare professional will interpret the CA 125 test results in the context of the individual's specific clinical situation.