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CA125 (Cancer Antigen 125)

Also referred as

Ovarian Cancer Marker

CA-125 Tumor Marker

CA 125 Blood Test

CA-125 Tumor Marker test

cancer Antigen 125 Test

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A CA125 (Cancer Antigen 125) test measures the amount of protein CA125 (Cancer Antigen 125) in blood. It is a tumor marker used to monitor certain cancers (particularly ovarian cancer) during and after therapy. In some high-risk individuals, the test may be used to look for early signs of an ovarian tumor. Serial measurements help to detect cancer recurrence and predict response to therapy. This test is not considered useful for cancer detection screening in the normal population.

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Understanding CA125 (Cancer Antigen 125)

CA125 is a protein found on the surface of ovaries, fallopian tubes, and body linings. High levels of CA125 in the blood might indicate ovarian cancer or other cancers like cervical, liver, pancreatic, lung, colon, stomach, biliary tract, uterine, fallopian tube, breast, and endometrial cancers. However, raised CA125 levels can also be caused by non-cancerous conditions such as menstruation, endometriosis, ovarian cysts, and pregnancy.

Your doctor may recommend this test if you experience symptoms suggestive of ovarian cancer, such as persistent abdominal or pelvic pain, bloating, difficulty eating, or urinary symptoms. It's also used to check for cancer recurrence or how well treatment is working in people with a history of ovarian cancer. Additionally, your doctor may recommend a CA125 (Cancer Antigen 125) test if you have risk factors such as increasing age, being overweight, having family members with cancer, or if you've never been pregnant.

Fasting is not needed to get a CA125 (Cancer Antigen 125) test done. However, talk to your doctor if you are taking any prescription medications or over-the-counter medications, as some of them may interfere with your test results. It is advisable not to get your test during menstruation or pregnancy as CA125 levels may show variations.

Test results may differ based on how the test is done. Values obtained with different methods cannot be used interchangeably for monitoring purposes. This test alone doesn't confirm or rule out cancer definitively because it can sometimes give wrong results, showing cancer when it's not there (false positives) or missing cancer when it is (false negatives). Therefore, talk to your doctor about your specific test results. Narrate your complete medical history to help them correlate your clinical and laboratory findings and formulate your treatment plan.

What does CA125 (Cancer Antigen 125) measure?

CA125 is a protein found in most ovarian cancer cells and some normal tissues. A CA125 (Cancer Antigen 125) test is commonly advised to detect ovarian cancer by measuring the amount of CA125 protein in the blood. A deranged level of CA125 antigen may indicate the presence of certain cancers, primarily ovarian cancer or other non-cancerous conditions, including endometriosis, pelvic inflammatory disease, ovarian cysts, etc.

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FAQs related to CA125 (Cancer Antigen 125)

Are there any non-cancerous conditions where high levels of cancer antigen 125 can be seen?

Yes, non-cancerous conditions such as pregnancy, menstruation, endometriosis (overgrowth of a uterine lining), ovarian cysts, pregnancy, uterine fibroids, liver disease, and inflammatory disease of the pelvis can show moderately high levels of cancer antigen 125.

Is a CA125 (Cancer Antigen 125) test a screening test for ovarian cancer?

No, a CA125 (Cancer Antigen 125) test should not be used for screening ovarian cancer in asymptomatic women as high levels of CA125 can be seen in cases of pregnancy, menstruation, uterine fibroids, endometriosis, pelvic inflammatory disease, etc.

What happens if my CA125 is high?

If your CA125 levels are high, the doctor can ask you to undergo a few more diagnostic tests before confirming any kind of cancer growth in the body. Serial and periodic testing in conjunction with clinical history and other imaging techniques will help reach a final clinical decision.

How can I lower my CA125 naturally?

Always consult your doctor if your test reports show a high amount of CA125 antigen. However, to naturally reduce the risk of developing cancer, you should exercise regularly, maintain a healthy lifestyle, try to avoid processed foods, and eat foods that are known to fight cancer cells (like berries, cabbage cauliflower, broccoli, etc.).

What are the symptoms associated with ovarian cancer?

Abdominal bloating or swelling, quickly feeling full when eating, sudden weight loss, discomfort in the pelvic area, fatigue, back pain, and changes in bowel habits, such as constipation and frequent need to urinate, are some common symptoms associated with ovarian cancer.

Who is at higher risk of ovarian cancer?

The risk of ovarian cancer increases steeply after 45 years of age. Apart from growing old, inherited genetic mutation, any previous history of cancer, and smoking are some other factors that put you at a greater risk of getting ovarian cancer. Women who have never given birth or have had trouble getting pregnant may also be at a higher risk of developing ovarian cancer.

How can I reduce the risk of ovarian cancer?

Some risk factors for ovarian cancer, like getting older or a family history, cannot be changed. But, women might be able to lower their risk slightly by maintaining a healthy weight or by monitoring hormone replacement therapy after menopause.

Content created by

Dr. Swati Gupta (Anand)

MBBS, MD Lab Medicine

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Last Updated

6th Oct 2025