Cancer & Tumor MarkersNo Fasting RequiredTurnaround: 12–24 hours

CA-125 (Cancer Antigen 125 — Ovarian Tumor Marker)

Also known as: Cancer Antigen 125, Carbohydrate Antigen 125, Ovarian Cancer Blood Test, CA 125 II

Parameters Measured in the Report

A breakdown of individual biomarkers and biological reference intervals typically found in your report:

Biomarker	Standard Range	Unit	What It Means
Serum CA-125 (Cancer Antigen 125)	Normal: < 35.0 (Suspicious in Post-Menopausal: > 35.0 Malignancy: > 65.0–1,000+)	U/mL	Epithelial glycoprotein tumor marker; primary surveillance marker for ovarian carcinoma.

* Note: Reference ranges may vary slightly between testing instruments and reagent kits. Always refer to the reference interval printed on your specific pathology report.

Clinical Focus

Circulating concentration of high-molecular-weight transmembrane glycoprotein antigen shed by coelomic and Müllerian epithelial tissues.

Sample & Specimen

Venous blood (Serum tube)

Fasting Protocol

No fasting required. Avoid scheduling blood draw during active menstrual period.

Turnaround Time

12–24 hours

What Is This Test?

Cancer Antigen 125 (CA-125) is a high-molecular-weight glycoprotein antigen naturally produced by tissues derived from coelomic epithelium (including the fallopian tubes, endometrium, endocervix, peritoneum, pleura, and pericardium). In oncological medicine, CA-125 is the primary serum biomarker used in the surveillance and management of **epithelial ovarian carcinoma** (which accounts for ~90% of ovarian malignancies). More than 80% of women with advanced ovarian cancer exhibit significantly elevated serum CA-125. However, because benign gynecological and inflammatory conditions also elevate CA-125, it is used for targeted surveillance and pelvic mass triage rather than general population screening.

Why Did Your Doctor Order This Test?

Physicians routinely prescribe the CA-125 in the following clinical scenarios:

Monitoring clinical response to chemotherapy and cytoreductive surgery in patients diagnosed with ovarian cancer

Surveillance for cancer recurrence after primary treatment: rising CA-125 often detects relapse months before tumors become visible on CT scans

Diagnostic evaluation of suspicious adnexal pelvic masses discovered on ultrasound, particularly in post-menopausal women

Risk of Ovarian Malignancy Algorithm (ROMA score) calculation combined with HE4 biomarker

Evaluating disease extent in severe pelvic endometriosis and adenomyosis

How to Prepare Before Your Test

Fasting Requirement: No fasting required. Avoid scheduling blood draw during active menstrual period.

No fasting is needed.
For pre-menopausal women: Blood collection should not occur during active menstrual bleeding, as menstruation naturally causes transient spikes in CA-125.

Understanding Your Results

What higher or lower readings generally mean in clinical practice:

If Values Are Higher Than Normal

A markedly elevated CA-125 (>65–1,000+ U/mL) in a post-menopausal woman with an ovarian mass or ascites carries high predictive value for ovarian cancer, requiring urgent gynecologic oncologist consultation. In pre-menopausal women, moderate elevations (35–150 U/mL) are frequently caused by benign conditions like endometriosis, uterine fibroids, pelvic inflammatory disease (PID), or liver cirrhosis.

If Values Are Lower Than Normal

A CA-125 level below 35.0 U/mL is normal. During post-treatment cancer surveillance, maintaining a low, stable CA-125 confirms successful disease remission.

Frequently Asked Questions

Why isn’t CA-125 used as a routine yearly screening test for all women?

CA-125 is not sensitive enough in early Stage 1 ovarian cancer (up to 50% of early cancers have normal CA-125) and is not specific enough in healthy pre-menopausal women (common benign conditions like periods, fibroids, and endometriosis cause false alarms).

What does a rising CA-125 mean after completing ovarian cancer chemotherapy?

Serial CA-125 tracking is extremely valuable. A progressive rise in CA-125 on two consecutive tests often heralds cancer recurrence 3 to 6 months before physical symptoms or CT scan lesions appear, giving oncologists a head start on second-line therapy.

Related Laboratory Tests

Tests frequently prescribed together or used as follow-up investigations:

CEA (Carcinoembryonic Antigen — Colorectal Tumor Marker)

Circulating concentration of oncofetal cell-surface glycoprotein involved in cellular adhesion, shed by gastrointestinal adenocarcinomas.

Alpha-Fetoprotein (AFP — Liver & Germ Cell Tumor Marker)

Circulating concentration of oncofetal plasma glycoprotein synthesized by fetal yolk sac and fetal hepatocytes.

Complete Blood Count (CBC / Hemogram)

Counts and evaluates red blood cells, white blood cells, hemoglobin, hematocrit, and platelets.

Liver Function Test (LFT / Hepatic Panel)

Bilirubin fractions, transaminases (ALT/SGPT, AST/SGOT), Alkaline Phosphatase (ALP), and proteins (Albumin, Globulin).

Medical & Diagnostic Disclaimer

This guide is published for educational and patient informational purposes only. It is not a substitute for professional medical evaluation, diagnosis, or clinical advice.

A laboratory result that falls slightly outside standard statistical reference intervals does not automatically indicate disease; conversely, a normal result does not guarantee the absence of medical conditions. Only your attending physician can interpret lab findings in the context of your medical history, physical exam, and symptoms.