Finding the right tests…
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Finding the right tests…
Hormonal
CA-125 is a protein that ovarian cancer cells often release into the blood, but it's also made by plenty of things unrelated to cancer, which is why this test needs careful context. Its main job in practice is watching someone already diagnosed with ovarian cancer — tracking whether treatment is working, or whether the disease has returned. Doctors also check it alongside an ultrasound when a pelvic mass shows up. What CA-125 is not is a general screening test: large trials found that testing average-risk women with no symptoms didn't reduce ovarian cancer deaths, and led to unnecessary surgery from false alarms. Endometriosis, fibroids, pelvic infection, your period, or even early pregnancy can raise CA-125 without any cancer involved.
This test measures CA-125 protein levels in a blood sample, reported in units per millilitre, using a standard venous draw with no fasting required. Because so many non-cancer conditions can raise this protein, your doctor reads the result together with your symptoms, menstrual history, and any pelvic imaging rather than as a stand-alone number. Serial CA-125 levels, drawn at intervals during or after cancer treatment, are generally more informative than any single reading, since the trend over time shows whether a tumour is responding.
CA-125 is a protein that ovarian cancer cells frequently release into the bloodstream in larger than normal amounts, which is why it was adopted early on as a tumour marker. The trouble is that plenty of ordinary, non-cancerous conditions raise it too, which limits how the test can responsibly be used.
It's tempting to think a simple blood test could catch ovarian cancer early in anyone, but large trials looking exactly at that question, reviewed by the National Cancer Institute, found no reduction in ovarian cancer deaths from routine CA-125 screening in average-risk women, alongside a real rate of unnecessary surgery from false alarms. That's why it isn't recommended as a general screening test.
Once ovarian cancer is already diagnosed, CA-125 becomes considerably more useful. Levels tend to fall as treatment works and rise again if the cancer returns, so tracking it over a series of tests gives a real signal. It's also sometimes checked alongside imaging when a pelvic mass is found, as one more piece of the picture rather than a stand-alone verdict.
- Not validated as a screening test in average-risk women - Many benign conditions can raise it - Most useful for monitoring known ovarian cancer over time
No. Large trials reviewed by the National Cancer Institute found that screening average-risk women with CA-125 didn't reduce ovarian cancer deaths, and it led to unnecessary surgery in some women with false-positive results, so it isn't recommended as a general screening test.
Plenty of non-cancer conditions raise CA-125, including endometriosis, pelvic inflammatory disease, uterine fibroids, and liver disease, according to MedlinePlus, along with everyday things like menstruation or early pregnancy.
Not completely. MedlinePlus notes CA-125 can be normal even in confirmed ovarian cancer, particularly in early-stage disease, so a normal result doesn't fully rule it out if other findings are concerning.
This page is general information about the test, not medical advice. Your own report's reference ranges apply — please discuss your results with your doctor.
It's mainly used to track whether treatment is working and to watch for a return of the cancer after treatment finishes, which MedlinePlus describes as its most common use.
A commonly used reference cutoff is around 35 U/mL, the threshold used in major screening trials reviewed by the National Cancer Institute, though it varies by lab and assay. Ranges vary by lab, so always check the specific reference range on your own report.
When a pelvic mass shows up on imaging, CA-125 is sometimes checked as one additional piece of information to help assess how concerning it might be, though it's never read in isolation from the imaging itself.
No specific fasting requirement is described for this test, but ask your doctor or the centre when you book.