CA-125 is a protein made by your body in response to many conditions — including cancer. It can be found on the surface of ovarian cells and on normal tissue. The doctor will draw and test your blood to determine if the level of CA-125 in your blood is higher than normal.

High levels of CA-125

While a high CA-125 level could be a sign of ovarian cancer there are other, nonmalignant conditions that can produce high levels of the protein. Even women known to have early stage ovarian cancer may not test for high levels of CA-125.While the test doesn't provide a definite answer, your physician may use the blood test as one more piece of evidence of the likelihood of cancer.  


CA-125 tests may be repeated over a period of time. Serial testing allows your health care team to determine if your CA-125 levels are increasing and how quickly. The rate at which CA-125 levels increase is a more accurate method of detecting the presence of ovarian cancer than a single CA-125 test.

Markers for rare forms of ovarian cancer

Reliable screening tests are not yet available for the two rarer forms of ovarian cancer, germ cell or stromal.The protein markers, human chorionic gonadotropin (HCG) and alphafetoprotein (AFP) are sometimes found in the blood of women with germ cell ovarian cancer.After they have undergone surgery and chemotherapy, blood tests showing the presence of these markers can be used to see if the cancer treatment is working or to identify a recurrence of the disease.

What to expect

  • Your doctor will refer you to a lab.
  • A blood sample is drawn just as for a variety of other lab tests.
  • The blood analysis assesses the amount of an antibody that recognizes an antigen in tumor cells.
The test
  • Blood is typically drawn from a vein, usually from the inside of the elbow or the back of the hand.
  • The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.
  • Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle.
  • The elastic band is removed from your arm. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.
  • When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation.