Understanding the CA 125 Blood Test
Being advised to have a CA 125 blood test can understandably raise concerns. In my practice, I reassure patients that CA 125 is a useful clinical tool in selected situations, but it is not a test that can diagnose ovarian cancer on its own.
Instead, CA 125 is interpreted alongside your symptoms, physical examination and imaging studies such as pelvic ultrasound to provide a more complete assessment.
What Is CA 125?
CA 125 (Cancer Antigen 125) is a protein found in the bloodstream. Some women with ovarian cancer have elevated CA 125 levels, but this marker can also increase in many non-cancerous conditions.
The CA 125 blood test measures the amount of this protein circulating in your blood.
Why Might Your Doctor Recommend a CA 125 Test?
Your doctor may recommend a CA 125 test to:
- Investigate symptoms that may suggest an ovarian condition
- Assess an ovarian cyst or pelvic mass together with ultrasound findings
- Monitor treatment response in women diagnosed with ovarian cancer
- Detect possible recurrence after treatment
- Support clinical assessment when appropriate
CA 125 is not recommended as a routine ovarian cancer screening test for women without symptoms or risk factors.
What Can Cause an Elevated CA 125 Level?
CA 125 levels may be elevated in:
- Ovarian cancer
- Endometriosis
- Uterine fibroids
- Pelvic inflammatory disease
- Menstruation
- Pregnancy
- Liver disease
For this reason, an elevated CA 125 level does not necessarily indicate cancer.
Can CA 125 Diagnose Ovarian Cancer?
No.
A CA 125 result alone cannot diagnose or exclude ovarian cancer. Some women with ovarian cancer may have normal CA 125 levels, while many women with elevated CA 125 levels have non-cancerous conditions.
Your doctor will interpret the result alongside your symptoms, pelvic examination and imaging studies to determine whether further evaluation is needed.
When Should You See a Doctor?
Arrange a medical review if you experience:
- Persistent abdominal bloating
- Pelvic or abdominal pain
- Feeling full quickly when eating
- Increased urinary frequency
- Unexplained weight loss
- Persistent changes that last more than a few weeks
These symptoms are often caused by conditions other than ovarian cancer, but they should be assessed if they persist.
Doctor's Insight
In my practice, I encourage women not to become overly concerned by a single CA 125 result. This blood test provides useful information in selected situations, but it is only one part of the overall assessment. Careful interpretation together with your symptoms and imaging studies allows us to make informed decisions about further investigation or treatment.
– Dr. Teh Boon Teong
Consultant in Internal Medicine
Evercare Medical Care Centre, Penang, Malaysia.
Frequently Asked Questions
It measures the level of Cancer Antigen 125, a protein that may be elevated in some ovarian conditions.
No. CA 125 alone cannot diagnose ovarian cancer and should always be interpreted together with other clinical findings.
Yes. Conditions such as endometriosis, fibroids, pelvic inflammatory disease, menstruation and pregnancy may increase CA 125 levels.
It may be used to investigate symptoms, assess an ovarian mass or monitor treatment after an ovarian cancer diagnosis.
It is generally not recommended as a routine screening test for women without symptoms or increased risk.