A CA-125 blood test is one way healthcare providers can monitor treatment for ovarian and other cancers. It’s also used as a screening tool for people at high risk of ovarian cancer. It doesn’t diagnose or detect cancer.
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A CA-125 test measures the amount of a protein called CA-125 (cancer antigen 125) in your blood. A high level of CA-125 can be a sign of ovarian cancer. Healthcare providers use this test as part of an overall approach to monitoring ovarian cancer, especially during and after treatment. But the test alone doesn’t diagnose or detect cancer. Many noncancerous conditions can raise CA-125 levels, too.
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A CA-125 blood test may be used to:
It’s also a way to screen for ovarian cancer in people who are at high risk. Some factors that put you at increased risk are:
This test shouldn’t be used if you have no symptoms or risk factors for ovarian cancer.
The test involves taking a small sample of your blood for testing. You may feel a slight prick or sting when the needle is placed in your arm. The blood draw should take a few minutes. You don’t need to do anything to prepare for a CA-125 test.
It doesn’t test for or diagnose cancer. It measures a protein in your blood that can be high if you have certain types of cancer. It’s mainly used for cancers of the:
The only risk is that involved with getting your blood drawn. You may feel lightheaded during the blood draw or notice a bruise afterward. In rare cases, infection or excessive bleeding occurs.
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Normal ranges may vary, and different labs may use different tests. Generally, levels higher than 35 units per milliliter are considered irregular. But high levels don’t mean you have cancer or that cancer has come back. Talk to your healthcare provider about your results to see if additional testing is needed.
Your provider will discuss what your test results mean for you. Even if the test shows high levels, more tests are necessary to diagnose cancer. The result of one test alone isn’t usually helpful. Your provider will order CA-125 tests in a series so they can identify changes in levels.
If you have ovarian cancer, a high CA-125 reading may mean cancer has returned. A lower score may indicate treatment is working.
Your CA-125 levels don’t tell your provider if the cancer has spread.
If the results are irregular, your provider will likely order additional tests to learn more. These could include an ultrasound, CT scan or MRI. They may also decide to repeat the CA-125 test later to see if the results change.
It’s not an accurate test on its own. Providers use it with other diagnostic tools. The test is known for having both false positives and false negatives because other conditions can lead to high CA-125 levels.
Some of those are:
No. It’s not reliable for detecting cancers of the bowel (intestines).
A CA-125 test is just one tool healthcare providers use to see if your cancer treatment is working. Talk to your provider about any concerns with the CA-125 test and what the results mean for your care. Only your provider should interpret your test results.
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Cleveland Clinic’s health articles are based on evidence-backed information and review by medical professionals to ensure accuracy, reliability and up-to-date clinical standards.
Cleveland Clinic’s health articles are based on evidence-backed information and review by medical professionals to ensure accuracy, reliability and up-to-date clinical standards.
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