Elevated levels of glycan antigen 125 (CA125) can be seen in many types of cancer, but the relationship between the two is not inevitable. Elevated levels of CA125 can also be seen in certain benign diseases, and there is no clear criterion for the relationship between elevated levels and the presence of cancer. CA125 is not only a specific marker for ovarian cancer, but also elevated in patients with fallopian tube adenocarcinoma, endometrial cancer, cervical cancer, pancreatic cancer, intestinal cancer, breast cancer, and lung cancer. 90% of the patients with ovarian cancer have serum CA125 associated with the progression of the disease, and therefore, it is mostly used for the detection of the disease and evaluation of the efficacy of treatment. Elevated CA125 level can also be seen in certain benign diseases, such as endometriosis, pelvic inflammatory disease, ovarian cysts, pancreatitis, hepatitis, cirrhosis, etc., but the positive rate is low, therefore, elevated CA125 level does not necessarily mean that you have cancer. Patients are advised to undergo further investigations in conjunction with their condition, such as abdominal CT, gastroenteroscopy, etc., and consult a specialist to decide on the next step of the treatment plan.