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 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. They 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 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?
Many things may affect your lab test results. These include the method each lab uses
to do the test. Even if your test results are different from the normal value, you
may not have a problem. To learn what the results mean for you, talk with your healthcare
Results are given in units per milliliter (U/mL). A normal CA 125 result is less than
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
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 provider may recommend that you see a gynecologic
oncologist. This is a cancer doctor who specializes in cancers of the female reproductive
How is this test done?
The test requires a blood sample, which is drawn through a needle from a vein in your
Does this test pose any risks?
Taking a blood sample with a needle carries risks that include bleeding, infection,
bruising, or feeling dizzy. When the needle pricks your arm, you may feel a slight
stinging sensation or pain. Afterward, the site may be slightly 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.