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Understanding the CA-125 Blood Test for Ovarian Cancer

Medically reviewed by Howard Goodman, M.D.
Written by Joanne Zamora
Posted on October 22, 2021

The CA-125 blood test is one of the tests that your health care provider may order if they suspect you may have ovarian cancer. Read on to learn more about this blood test and what its results may signify.

What Is the CA-125 Blood Test?

The CA-125 blood test measures the amount of a specific protein called cancer antigen 125, or CA-125, in a person’s blood. Elevated CA-125 levels can suggest ovarian cancer, but they can also be caused by many benign conditions. Depending on the amount found in your blood — along with factors like your age, symptoms, and ultrasound results — oncologists (doctors who treat cancer) can tell if there’s a high probability that you have ovarian cancer.

Doctors may use CA-125 testing to screen for early-stage ovarian cancer in people who have a high risk of ovarian cancer. This could include people who have a family history of breast or ovarian cancer in multiple family members and who themselves have a BRCA or other genetic mutation. If you have a family history of ovarian cancer, discuss screening protocols with your gynecologist or other health care provider.

CA-125 testing is also commonly used to monitor the progress of ovarian cancer during and after treatment.

Why Is It Important to Detect and Monitor CA-125?

It’s important to detect the amount of CA-125 in your blood because it will serve as a tumor marker if you have ovarian cancer. When doctors spot an elevation in CA-125 levels, they may recommend that you have other confirmatory tests so they can make an accurate diagnosis.

After making an ovarian cancer diagnosis, your health care team will proceed with the appropriate treatment to try to control the ovarian cancer cells. They will regularly check the CA-125 values in your bloodstream to monitor if your treatment needs to be updated or modified.

Monitoring and Adjusting Cancer Treatment

Testing your CA-125 levels can help your health care team determine how well your course of treatment is working. If your CA-125 levels begin to decrease, this suggests that the cancer is responding to treatment. Your team will continue with the current treatment and regularly monitor your body’s response. If your CA-125 value increases or plateaus, this indicates a lack of response to treatment. Your team will need another approach to treat your cancer.

Detecting Cancer Recurrence

The CA-125 blood test can also be used to monitor people who are in remission. Your doctor may recommend periodic testing to help detect a cancer recurrence. CA-125 testing while you’re in remission can help to detect any cancerous cells that have reemerged after treatment. If these cells are present, the CA-125 test can help your doctor spot them early.

Can You Have Ovarian Cancer Without High CA-125 Levels?

Low CA-125 levels in people with ovarian cancer are possible. This is why CA-125 results are usually just the first step in ovarian cancer diagnosis. After getting the results of this test, oncologists perform other tests to confirm the presence of ovarian cancer.

Do High CA-125 Levels Always Mean Ovarian Cancer?

You can have an elevated CA-125 level even if you don’t have ovarian cancer. This is known as a false positive. Other conditions that can present with heightened CA-125 levels in an otherwise healthy person include:

  • Menstruation
  • Pregnancy (normal or ectopic)
  • Endometriosis
  • Uterine fibroids
  • Tuberculosis
  • Pneumonia
  • Peritonitis
  • Diverticulitis
  • Inflammatory bowel disease
  • Pancreatitis
  • Renal failure
  • Liver disease
  • Heart failure
  • Infection of the ovaries, uterus, or fallopian tubes (pelvic inflammatory disease)
  • Lung cancer or a cancer affecting the abdominal cavity, including endometrial, fallopian tube, breast, and pancreatic cancer

CA-125 Reference Range and Its Significance

The normal value for CA-125 is less than 46 units per milliliter. While high levels of CA-125 are a relatively strong indicator for ovarian cancer, they don’t automatically mean that you have ovarian cancer. If you have elevated CA-125 levels, your doctor will recommend other tests to diagnose your condition more accurately.

Preparing for the Test

Having a doctor recommend a CA-125 test can induce some anxiety, especially if you know someone who has had ovarian cancer. Fortunately, there are ways to ease your anxiety about the CA-125 test.

If you have questions regarding the test, ask your doctor and other related professionals. Don’t hesitate to ask questions regarding the nature of the test and what to expect before, during, and after.

You may also turn to friends or loved ones for comfort. Finding those who help keep you calm and can help you work through your anxieties can make a world of difference.

At the end of the day, with the right information and mindset, you can get through the CA-125 test in no time.

Meet Your Team

You don’t have to be alone in your journey with ovarian cancer. If you have ovarian cancer or are caring for someone with it, join MyOvarianCancerTeam. Here, you can find the emotional support you need, as well as practical tips from a growing community that understands life with ovarian cancer.

Have you had the CA-125 blood test? Share your experience in the comments below or by posting on MyOvarianCancerTeam.

Posted on October 22, 2021
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Howard Goodman, M.D. is certified by the American Board of Obstetrics and Gynecology and specializes in the surgical management of women with gynecologic cancer. Review provided by VeriMed Healthcare Network.. Learn more about him here.
Joanne Zamora is a pharmacist with nearly a decade of clinical experience in a tertiary hospital setting. Learn more about her here.

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