Cancer Marker

CA-125 Test: Uses & Limitations

CA-125 is used to monitor ovarian cancer treatment, but it's an unreliable screening test due to many benign causes of elevation — a crucial point for anyone considering a private CA-125 test.

Normal range
<35 U/mL (varies by lab)
Main use
Ovarian cancer monitoring
Screening role
Not recommended for general population
Also raised by
Endometriosis, fibroids, periods, pregnancy

Non-Cancer Causes of Elevated CA-125

CauseNotes
MenstruationCan cause temporary elevation
EndometriosisCommon cause of raised CA-125
Uterine fibroidsFrequently elevates levels
Pregnancy (early)Can raise levels
Pelvic inflammatory diseaseInflammatory elevation
Liver disease, heart failureNon-gynaecological causes

Why CA-125 Is Not a Reliable Screening Test

Large studies (including the UK Collaborative Trial of Ovarian Cancer Screening) found that using CA-125 alone or combined with ultrasound to screen average-risk women did not reduce ovarian cancer deaths and led to unnecessary surgeries from false positives. It is NOT recommended as a population screening test.

When CA-125 Is Useful

Family History Changes the PictureFor women with a strong family history of ovarian or breast cancer (especially with BRCA1/2 mutations), a different risk-based approach with genetic counselling and possibly risk-reducing surgery is more appropriate than routine CA-125 screening.
Can I just get a CA-125 test to check for ovarian cancer?
You can request it, but be aware it has poor accuracy as a standalone screening test in average-risk women — a normal result doesn't rule out cancer, and an abnormal result is often due to benign conditions.
Why does my CA-125 fluctuate with my period?
CA-125 can rise during menstruation due to normal shedding of the womb lining, which is one reason it's not reliable as an isolated screening measure.
What symptoms should prompt ovarian cancer investigation regardless of CA-125?
Persistent bloating, feeling full quickly, pelvic pain, and needing to urinate urgently/frequently, especially if new and persistent (>12 times a month), should prompt medical assessment regardless of any test results.
Medical Disclaimer: This page is for general education only and does not replace professional medical advice. Always consult a qualified healthcare provider.