Cancer Antigen 125 serum test measures the level of a protein called CA 125 in the blood. This protein is found on the surface of some ovarian cancer cells. Its level in the blood can be used to help diagnose and monitor ovarian cancer. It is present in small amounts in the blood of healthy women. When ovarian cancer is present, the level of CA 125 in the blood is usually higher than normal.

Who Needs to Undergo a CA 125 Blood Test?

Your doctor may prescribe CA 125 test if –

1. You are at a higher risk of ovarian cancer. This may be due to
   • Specific inherited genes like BRCA 1 or BRCA 2
   • A family history of ovarian cancer
   • Having previously suffered from cancer of the breast, uterus, or colon.
2. You are undergoing treatment for ovarian cancer. CA125 levels can help determine the effectiveness of treatment. Usually, decreasing levels means that the treatment is working.
3. Regular screening to check if cancer has come back.
4. General cancer screening or health checkup

Preparing For CA 125 Blood Test

Although there are no special requirements for the CA 125 blood test preparation, keep the following things in mind:

• Inform your doctor about any medications you are consuming.
• Intimate your doctor regarding any allergies you may have.
• If there has been an incident of an animal bite, inform your doctor about it. Antibodies would be present in your body because of the incident that may interfere with the test results.

What do the results mean?

Your doctor will review your CA-125 test results along with other information about your condition. Together, you can discuss how your results affect your diagnosis, treatment, and need for more testing.

In general:

• If you are being treated for ovarian cancer, and the results of several tests show that your CA-125 levels are going down, it usually means that the treatment is helping. If your levels go up or stay the same over time, it may mean that the treatment isn’t working.
• If you have finished your treatment for ovarian cancer and your CA-125 levels begin to increase over time, your cancer may be coming back.
• If you have a high risk for ovarian cancer or have a suspicious pelvic lump, a high CA-125 levels could be a sign of cancer. Your provider will usually order more tests to make a diagnosis.

A high CA-125 level doesn’t always mean cancer. Other conditions may increase CA-125, including:

• Endometriosis
• Pelvic inflammatory disease (PID)
• Uterine fibroids
• Liver disease
• Pregnancy
• Your menstrual period, at certain times during your cycle

A normal CA-125 test result doesn’t rule out ovarian cancer. That’s because CA-125 levels may be low in the early stages of cancer. And not everyone with ovarian cancer makes high levels of CA-125.

Talk with your doctor if you have questions about your results.