Also Known As
CA-125
Formal Name
Cancer Antigen 125
This article was last reviewed on
This article waslast modified on
15 January 2018.
At a Glance
Why Get Tested?

To monitor treatment for ovarian cancer

When To Get Tested?

Before starting therapy for ovarian cancer or if at high risk for developing ovarian cancer, and at intervals during and after treatment. CA 125 may also be request by your GP if you have persistent or frequent symptoms that may be caused by ovarian cancer.

Sample Required?

A blood sample taken from a vein in the arm

Test Preparation Needed?

None

On average it takes 7 working days for the blood test results to come back from the hospital, depending on the exact tests requested. Some specialist test results may take longer, if samples have to be sent to a reference (specialist) laboratory. The X-ray & scan results may take longer. If you are registered to use the online services of your local practice, you will be able to access your results online.

If the doctor wants to see you about the result(s), you will be offered an appointment. If you are concerned about your test results, you will need to arrange an appointment with your doctor so that all relevant information including age, ethnicity, health history, signs and symptoms, laboratory and other procedures (radiology, endoscopy, etc.), can be considered.

Lab Tests Online-UK is an educational website designed to provide patients and carers with information on laboratory tests used in medical care. We are not a laboratory and are unable to comment on an individual's health and treatment.

Reference ranges are dependent on many factors, including patient age, gender, sample population, and test method, and numeric test results can have different meanings in different laboratories.

For these reasons, you will not find reference ranges for the majority of tests described on this web site. The lab report containing your test results should include the relevant reference range for your test(s). Please consult your doctor or the laboratory that performed the test(s) to obtain the reference range if you do not have the lab report.

For more information on reference ranges, please read Reference Ranges and What They Mean.

What is being tested?

CA 125 is a protein often found on the surface of ovarian cancer cells and in some normal tissues. It is used as a marker for ovarian cancer. However, CA 125 levels may also be high in other types of non-cancerous conditions, including menstruation, pregnancy, and pelvic inflammatory disease.

How is the sample collected for testing?

Blood is taken from a vein in the arm.

Is any test preparation needed to ensure the quality of the sample?

None required.

Accordion Title
Common Questions
  • How is it used?

    CA 125 is mainly used to monitor therapy during treatment for ovarian cancer. CA 125 is also used to detect whether cancer has come back after treatment is complete. This test is sometimes used to follow women who are at high-risk because they have a family history of ovarian cancer but who do not yet have the disease. CA 125 is also recommended together with pelvic ultrasonography in women (especially if over 50 years), aged over 50 years who have persistent, continuous or worsening unexplained tummy pain, bloating, feeling full and/or loss of appetite or problems with urination and in whom a doctor is concerned after examining the tummy.

  • When is it requested?

    Before a patient starts treatment for ovarian cancer, the doctor will measure CA 125 to be able to compare it with future measurements. During therapy, doctors use CA 125 testing, at intervals, to follow the response to therapy. CA 125 may also be measured several times after therapy is completed to catch any early signs of the cancer’s return.CA 125 may also be requested by your GP if you have persistent or frequent symptoms (e.g. unexplained tummy pain, bloating, feeling full and/or loss of appetite or problems with urination) to determine if you require an ultrasound scan of the abdomen and pelvis.

  • What does the test result mean?

    If CA 125 levels fall during therapy, this generally indicates that the cancer is responding to treatment. If CA 125 levels rise, the cancer may not be responding to treatment. High CA 125 levels after treatment is complete may indicate that the cancer has come back. In women without a diagnosis of ovarian cancer a raised CA125 may indicate the need for an ultrasound of the abdomen and pelvis.

  • Is there anything else I should know?

    A CA 125 result that is higher than normal does not always mean a patient has overian cancer. CA 125 can be high in many normal or benign conditions (for example, pregnancy, menstruation, endometriosis and pelvic inflammatory disease).

  • Is CA125 always increased in ovarian cancer?

    No, not all ovarian cancers  have increased levels of CA 125. Elevated levels have been found in about 80% of women with ovarian cancer.

  • My CA 125 is elevated. Does it mean I have cancer?

    No. CA 125 may be elevated in several other conditions and diseases. CA 125 may normally be increased in early pregnancy and during menstruation. It can also be increased in diseases such as pelvic inflammatory disease or endometriosis and sometimes in hepatitis and cirrhosis of the liver.

  • Does ovarian cancer run in families?

    Family history is a risk factor for ovarian cancer. If you have close family members who have had ovarian cancer, you are at higher risk than someone who has no family history of the disease. Make sure your doctor knows about your family medical history.