As of 2012, the cancer antigen 125 or CA-125 is a blood test that can cost about $80, according to Fox News. This blood test, which measures the amount of the protein CA-125 in the blood, is often ordered for monitoring women diagnosed with ovarian cancer, relates the National Institutes of Health's Medline Plus. However, a high level of CA-125 does not necessarily mean that an undiagnosed woman has ovarian cancer because there are many other conditions that may cause an elevated level of this protein, relates the Mayo Clinic.
Some other conditions that also can cause a high level in CA-125 include endometriosis and uterine fibroids. Because of this, the test is not often recommended for women who have an average risk for ovarian cancer, reports the Mayo Clinic. The test may be more appropriate for women who are at a higher risk for this disease and also have BRCA 1 and BRCA 2 gene mutations. A normal level for CA-125 is less than 35 U/mL.