CA-125 (Ovarian Cancer Marker)
Measures CA-125 protein levels to help monitor ovarian cancer treatment or screen individuals at high risk.
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Lab testing services linked from this site are not available to residents of Alaska, Arizona, or Hawaii, unless otherwise noted on the lab's own website.
This publication is not intended to solicit the purchase of laboratory testing from any individual consumer.
What this test measures
CA-125 (cancer antigen 125) is a protein found on the surface of many cells and released into the bloodstream in measurable quantities. Elevated CA-125 levels are detected in more than 80% of advanced epithelial ovarian cancers, making it the most widely used blood marker for monitoring this disease. However, CA-125 is not specific to ovarian cancer: it is also expressed by cells in the fallopian tubes, uterine lining, and peritoneum, and can be elevated in a range of non-cancerous conditions.
Benign causes of elevated CA-125 include endometriosis, ovarian cysts, pelvic inflammatory disease, cirrhosis, hepatitis, and even early pregnancy. Because of this limited specificity, CA-125 is not recommended as a general screening test for ovarian cancer in the average-risk population. Its primary clinical value lies in monitoring treatment response and detecting recurrence in patients who have already been diagnosed with ovarian cancer, and in evaluating pelvic masses in combination with imaging in individuals who present with suspicious findings.
Who should consider this test
You might consider this test if you are experiencing any of the following:
- Individuals with a family history of ovarian cancer, particularly those with BRCA gene mutations or multiple affected relatives
- Those being monitored during or after treatment for ovarian, fallopian tube, or primary peritoneal cancer
- Postmenopausal individuals with unexplained pelvic symptoms or suspicious pelvic masses
- Patients with a personal history of ovarian cancer who need regular surveillance for recurrence
- Those with genetic predisposition syndromes associated with increased ovarian cancer risk
What to expect
Preparation
No fasting is required. Stop biotin supplements at least 72 hours before collection. Avoid testing during menstruation when possible, as CA-125 levels can be elevated during menses. Schedule testing at least one week after menstrual period completion for most accurate results.
Sample Type
A simple blood draw from a vein in the arm
Collection
A healthcare professional will clean the collection site, insert a small needle into a vein, and draw the blood sample. The process typically takes just a few minutes.
Turnaround
Results are typically available within 1-2 business days after the sample reaches the laboratory
Understanding your results
The standard reference range places normal CA-125 below 35 U/mL (units per milliliter). A level above this threshold prompts further evaluation but does not confirm cancer on its own, given the number of benign conditions that can produce elevations. In patients being monitored for known ovarian cancer, the trend of CA-125 values over time is more clinically significant than any single reading: a declining trajectory during treatment suggests response, while a rising pattern may indicate recurrence. Healthcare providers interpret CA-125 alongside imaging studies, clinical symptoms, and pathology findings to guide management decisions.
| Population | Reference Range | Notes |
|---|---|---|
| Adults (All) | 0-35 U/mL | Normal range for healthy individuals |
Reference ranges shown are general guidelines. Your lab report will include the specific reference range used by the laboratory that processed your sample, which is the authoritative range for interpreting your results.
What does a “Low” result mean?
CA-125 levels within the normal range (0-35 U/mL) typically indicate the absence of the conditions that commonly elevate this marker. However, normal levels do not rule out recurrence in those with a history of ovarian cancer. Some individuals with early-stage ovarian cancer may have normal CA-125 levels. It is possible to get a normal ovarian cancer marker range in results, and a normal report does not rule out the possibility of cancer. For this reason, healthcare providers rely on multiple diagnostic approaches including imaging studies and physical examination alongside CA-125 testing.
What does a “High” result mean?
Anything over 35 U/mL is considered elevated. Serum CA 125 is elevated in approximately 80% of women with advanced epithelial ovarian cancer, but the assay sensitivity is suboptimal in early disease stages. However, elevated CA-125 levels may indicate various conditions beyond ovarian cancer. Elevated serum CA-125 levels have been reported in individuals with a variety of nonovarian malignancies including cervical, liver, pancreatic, lung, colon, stomach, biliary tract, uterine, fallopian tube, breast, and endometrial carcinomas, as well as benign conditions including cirrhosis, hepatitis, endometriosis, first trimester pregnancy, ovarian cysts, and pelvic inflammatory disease. In individuals already diagnosed with ovarian cancer, rising levels may suggest disease progression or treatment resistance.
Privacy & confidentiality
All test orders are authorized and results reviewed by an independent, board-certified physician who is not the patient's personal doctor. Your CA-125 test results are completely confidential and handled with the utmost discretion. Results are __not reported to your doctor__ unless you specifically choose to share them. This test is __not part of your medical records__ maintained by your healthcare provider or health system. The test __will not appear on insurance statements__ or explanation of benefits (EOB) forms, ensuring complete privacy. Your results are not shared with employers, insurance companies, or any third parties. This confidential testing allows individuals to monitor their health status privately, particularly important for sensitive cancer marker screenings where individuals may want to assess their risk or monitor their condition discreetly before involving their healthcare provider.
Frequently asked questions
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Last reviewed: April 2026
CPT Code: 86304
This test may not be available in: NY, NJ, RI
This page is for informational purposes only and does not constitute medical advice. Always consult with a healthcare provider regarding any health concerns. LevelPanel does not diagnose, treat, or prescribe.
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LevelPanel has no business or affiliate relationship with Quest or LabCorp. These links are provided as a public service.
Lab testing services linked from this site are not available to residents of Alaska, Arizona, or Hawaii, unless otherwise noted on the lab's own website.
This publication is not intended to solicit the purchase of laboratory testing from any individual consumer.
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