CA 125 Test - Normal Range

A CA 125 test measures the amount of the protein CA 125 (cancer antigen 125) in your blood. Cancer Antigen 125 (CA-125) is a protein that is present on the surface of most, but not all, ovarian cancer cells.

CA125 test is used to monitor treatment for ovarian cancer or to detect recurrence, sometimes to evaluate a lump located in the pelvic area (pelvic mass). It’s not recommended for screening but sometimes ordered to help detect early ovarian cancer in those identified as being at high risk.

Test Preparation

CA125 is a blood test with a blood sample usually from arm vein. No preparation is needed for the test.


Normal range of CA-125 is less than 35 U/mL in most labs, since 95% healthy women are in this range.

If CA-125 levels fall during therapy, this generally indicates that the cancer is responding to treatment. If CA-125 levels rise or stay the same, then the cancer may not be responding to therapy. High CA-125 levels after treatment is complete may indicate that the cancer has come back.

If a woman who has been diagnosed with ovarian cancer has a baseline CA-125 level that is normal, then the test is not likely to be useful to monitor her ovarian cancer. In this case, the ovarian cancer may not be producing CA-125 and is not a good marker of disease progression.

In a woman with a pelvic mass, and in a woman with a high risk for developing ovarian cancer, a significantly elevated CA-125 is a concern but does not necessarily indicate ovarian cancer. This finding would prompt further testing and evaluation.




* The Content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.