CA-125 (Cancer Antigen 125) Tumor Marker
This blood test measures the levels of CA-125, a protein produced by some cancerous and some noncancerous cells in the body.
["CA-125 helps monitor ovarian cancer and other conditions, but it is not a definitive test for cancer alone."]
Key facts at a glance
- LOINC
- 50775-6
- Short code
- CSF-CA125
- Synonyms
- Cancer Ag125 CSF-aCnc
- Category
- chemistry
- Sample
- csf
- Container
- Sterile, screw-capped, leak-proof polypropylene collection tube for CSF specimens
- Units
- N/A
- Critical range
- 0.5 N/A – —
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–99 years
- Method
- Immunoassay (Electrochemiluminescence Immunoassay or Chemiluminescent Immunoassay)
- CPT
- 86304
- SNOMED
- 395132000
- Specimen volume
- 1-2 mL of cerebrospinal fluid
- Stability
- Room temperature: 2 hours; Refrigerated (2-8°C): 48 hours; Frozen (-20°C or below): 3 months for CA 125 determination
- Hemolysis max
- 200
- TAT
- 24–72 hours
- Order
- routine
What Is CA-125 Used For?
CA-125 is primarily used as a screening and monitoring tool for ovarian cancer. It may also be checked in patients with other gynecologic cancers, such as endometrial or cervical cancer, or in those with conditions like endometriosis or pelvic inflammatory disease. Doctors may also use it to track response to treatment in certain cancers.
How Is the Test Performed?
A blood sample is taken from a vein, usually in your arm. The sample is then sent to a lab for analysis. CA-125 levels are measured using an immunoassay method to detect the protein in your blood.
When Might You Need This Test?
You might need a CA-125 test if you have symptoms like abdominal pain, bloating, or unexplained weight loss. It may also be ordered as part of routine monitoring for ovarian cancer or other conditions where CA-125 levels are relevant.
What Do Results Mean?
Elevated CA-125 levels can indicate ovarian cancer or other conditions affecting ovarian tissue. However, CA-125 alone is not enough to diagnose cancer. Results may also be higher in non-cancerous conditions, so they should be interpreted by your healthcare provider in the context of your medical history and other test results.
Reference range
CA 125 is normally not detectable or present at very low concentrations in cerebrospinal fluid. Reference values in CSF have not been firmly established; results should be interpreted in conjunction with clinical findings and imaging studies.N/A
No special patient preparation required. Fasting is not necessary for CSF CA 125 testing.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Clinical Significance: CA-125 plays a key role in ovarian cancer detection and surveillance. While it is not specific to cancer, rising levels often prompt further investigation, such as imaging or biopsy. It is also used to assess recurrence or treatment effectiveness in certain cancers.
Short name
CA-125 Blood Test
Frequently asked questions
Why might my CA-125 test be ordered?
Can CA-125 levels be affected by other health conditions?
How often should I get a CA-125 test?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 17, 2026. · Read our editorial policy