CA 125

Does this test have other names?

Cancer antigen 125, glycoprotein antigen, ovarian cancer antigen

What is this test?

This test looks for the protein CA 125 in your blood. CA 125 is called a biomarker. This means that it might mean disease is present. CA 125 is often higher in many women with ovarian cancer.

Healthcare providers may use this test to look for ovarian cancer in women who may be at high risk because of family history or symptoms. It would be used along with other tests. Healthcare providers may also use this test to see if treatment is working. Or they may use it to find out if cancer is coming back after treatment.

CA 125 is also higher in some conditions that are not cancer. This means that CA 125 is not a good blood test to screen all women for ovarian cancer.

Why do I need this test?

You may have this test if you have symptoms of ovarian cancer or a family history of it. This test may be done as part of your diagnosis.

You may also have this test if you have already been diagnosed with ovarian cancer and your healthcare provider wants to see if treatment worked. You may get this test done before and during treatment.

You may also have this test if you've already been treated for ovarian cancer and your healthcare provider needs to find out if the cancer has come back. Measuring CA 125 is one of the best ways to figure out if ovarian cancer has come back after treatment.

What other tests might I have along with this test?

Your healthcare provider will likely order other tests, depending on your stage of the disease. These include other blood tests and imaging studies, like an ultrasound, CT scan, or MRI.

What do my test results mean?

Test results may vary depending on your age, gender, health history, and other things. Your test results may be different depending on the lab used. They may not mean you have a problem. Ask your healthcare provider what your test results mean for you.

Results are given in units per milliliter (U/mL). A normal CA 125 result is less than 35 U/mL.

But it's important to know that having a higher CA 125 result doesn't mean you have cancer. Many conditions other than cancer can cause CA 125 to rise. These include inflammatory disease, recent surgery, fibroids, your menstrual cycle, and an ectopic pregnancy.

And having a normal CA 125 result doesn't mean you don't have ovarian cancer. Some women with early ovarian cancer have a normal CA 125 level.

One higher than normal or normal CA 125 test result is not as important as a series of CA 125 blood tests over time.

If you have a high CA 125 level, your healthcare provider may recommend that you see a gynecologic oncologist. This is a cancer healthcare provider who specializes in cancers of the female reproductive system.

How is this test done?

The test is done with a blood sample. A needle is used to draw blood from a vein in your arm or hand.

Does this test pose any risks?

Having a blood test with a needle carries some risks. These include bleeding, infection, bruising, and feeling lightheaded. When the needle pricks your arm or hand, you may feel a slight sting or pain. Afterward, the site may be sore.

What might affect my test results?

Pregnancy and your menstrual cycle can affect your results. Some medicines used to treat ovarian cancer can also affect your results.

How do I get ready for this test?

You don't need to prepare for this test. Be sure your healthcare provider knows about all medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illegal drugs you may use.