CA 125 is a blood test that measures the level of a protein known as cancer antigen 125, which is typically produced by cells in the uterus and ovaries. CA 125 is considered a biological marker that may increase in certain conditions, including ovarian cancer, but it can also rise due to non-cancerous conditions such as pelvic inflammation, ovarian cysts, or even during the menstrual cycle. This test is used as part of a comprehensive evaluation for patients who present with symptoms that may suggest ovarian cancer, such as pelvic pain, abdominal bloating, or changes in urinary habits. Although CA 125 is not a definitive diagnostic test, it can help doctors determine the extent of the disease and monitor treatment effectiveness after a cancer diagnosis. It is important for CA 125 results to be interpreted with a specialist, as many factors can influence the levels, including personal medical history and genetic factors. Additional tests or imaging may be recommended to confirm a diagnosis or monitor changes in health status.