CA 125

  • Medical Author:
    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

  • Medical Editor: William C. Shiel Jr., MD, FACP, FACR
    William C. Shiel Jr., MD, FACP, FACR

    William C. Shiel Jr., MD, FACP, FACR

    Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

Cancer 101: Cancer Explained

Ovarian Cancer Testing

CA 125

The CA-125 is a blood test that is often, but not always, elevated with ovarian cancer. If a postmenopausal woman has a mass and an elevated CA-125, she has an extremely high risk of having a cancer. However, in younger women, CA-125 is extraordinarily inaccurate. It is elevated by a large number of disease processes, including but not limited to, diverticulitis, pregnancy, irritable bowel syndrome, appendicitis, liver disease, stomach disease, and more. No one should get this test done unless they actually have a mass, or their doctor has some reason to get it. It should not be drawn just to see the level since it is not a reliable screening test for ovarian cancer.

Quick GuideOvarian Cancer Symptoms, Signs, Stages

Ovarian Cancer Symptoms, Signs, Stages

What is CA 125 test? What is a tumor marker?

CA 125 is a protein that is a so-called tumor marker or biomarker, which is a substance that is found in greater concentration in tumor cells than in other cells of the body. In particular, CA 125 is present in greater concentration in ovarian cancer cells than in other cells. It was first identified in the early 1980s, and the function of the CA 125 protein is not currently understood. CA stands for cancer antigen. CA 125 is often measured as a blood test.

How is CA 125 measured?

CA 125 is usually measured from a venous blood sample. It can also be measured in fluid from the chest or abdominal cavity. The tests currently in use are all based upon the use of an antibody that is directed against the CA 125 protein (monoclonal antibody technique).

In 1991, an improved version of the test was introduced and is sometimes denoted as CA 125 - II. The numerical figure of the second generation test results may be higher or lower than a first generation test. The first generation test is no longer used. When comparing multiple CA 125 test results over time, it can be important to know which method was used.

What is the normal range for CA 125?

The normal values for CA 125 may vary slightly among individual laboratories. In most laboratories, the normal value is 0 to 35 units/ml.

Medically Reviewed by a Doctor on 7/26/2016

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