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CA-125
A protein marker most often checked when an ovarian mass is found. It also rises in benign conditions — endometriosis, inflammation, menstruation.
Other names: CA-125, Cancer Antigen 125Section: Tumor markers
Updated: August 31, 2026·MedProtect editorial team Reference information — not a diagnosis or a prescription
In shortCA-125 is a marker checked when evaluating ovarian masses and when monitoring ovarian cancer treatment. A typical cut-off is 35 U/mL. It also rises with endometriosis, inflammation and during menstruation — it is unsuitable for screening healthy women.
Reference ranges
Group
Reference range
Women and men (typical cut-off)
up to 35 U/mL
The source states: a level above 35 U/mL is considered abnormal. Assays differ between laboratories. Reference ranges vary between laboratories and assays — use the range printed on your own lab report.
Check your value
Enter the number from your lab report — see how it compares with the typical range. Mind the units shown in the chosen row.
A rough comparison with a typical range, not a diagnosis. Reference ranges vary between laboratories — check the range on your own report and let a clinician interpret the result.
What this marker is
CA-125 (cancer antigen 125) is a glycoprotein produced in small amounts by the lining cells of the abdominal and chest cavities. In practice it is most often ordered for women with a detected ovarian mass and to monitor treatment of ovarian cancer.
The marker's key trait is low specificity: CA-125 rises with endometriosis, fibroids, pelvic inflammatory disease, during menstruation and pregnancy, and with cirrhosis and peritonitis. It is therefore not used to screen healthy women: its place is assessing an already-found mass together with ultrasound and tracking therapy in patients with a confirmed diagnosis.
When it is high
EndometriosisOne of the most common benign causes of a moderate CA-125 rise.
Menstruation and pregnancyA physiological rise — the test is best taken outside menstruation.
Pelvic inflammatory diseaseAdnexitis, peritonitis and other abdominal inflammation.
Ovarian and other cancersA steady marked rise calls for combined assessment with ultrasound and a gynecologist's exam.
Liver diseaseCirrhosis and chronic hepatitis can moderately raise the marker.
When it is low
Normal findingA low CA-125 is the expected result; a decrease has no clinical meaning.
What can skew the result
These factors can shift the value without any disease — worth considering before a retest:
Blood from a vein. Best taken 2–3 days after menstruation ends — the level is physiologically higher during it. No special diet. For trends, use the same lab: assays and calibrations differ.
When a retest makes sense
For a moderate rise — 2–4 weeks after menstruation ends; when monitoring a mass or treatment — on the gynecologist's schedule.
Who usually reviews this result
A result outside the reference range is usually reviewed by: gynecologist; with a confirmed diagnosis — gynecologic oncologist. Bring your lab report and any previous results to the appointment.
Names used on lab reports
Your report may use any of these names: CA-125Cancer antigen 125CA 125
Units
Measured in: U/mL
Several markers on your report?
See how MedProtect explains results in the app: the whole report, a check of the recognized values, and a clear breakdown.
No. A small excess is far more often explained by endometriosis, inflammation or menstruation. The gynecologist will read it together with ultrasound and may repeat the test over time.
Why take CA-125 at all?
The marker helps evaluate an already-found ovarian mass (with ultrasound, it informs risk) and is invaluable for tracking treatment in patients with a confirmed diagnosis.
Can I test 'just in case'?
The test does not suit screening healthy women: it misses early stages and often raises false alarms. A gynecologist decides on testing by indication.
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