Cancer Antigen 125 (CA-125) Fluid Concentration (Serum/Plasma)
This test measures the concentration of CA-125, a protein linked to certain types of ovarian cancer and other gynecologic or non-gynecologic malignancies.
["CA-125 levels help monitor cancer progression or response to treatment in certain cancers."]
Key facts at a glance
- LOINC
- 99382-4
- Short code
- CA50BF
- Synonyms
- Cancer Ag50 Fld-aCnc
- Category
- chemistry
- Sample
- serum
- Container
- Serum separator tube (SST) or red-top clot activator tube; acceptable body fluid collection container per source fluid type.
- Units
- N/A
- Ref low
- 0
- Ref high
- 25
- Critical range
- 0.5 N/A – —
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- ≥ 18 years
- Method
- Immunoassay (chemiluminescent or enzyme-linked)
- Specimen volume
- 1-2 mL of serum or body fluid
- Stability
- Serum stable at room temperature for 8 hours; refrigerated (2-8°C) for 7 days; frozen (-20°C) for up to 3 months
- Hemolysis max
- 100
- Lipemia max
- 200
- Icterus max
- 40
- TAT
- 24–72 hours
- Order
- routine
What Is CA-125 Used For?
CA-125 is primarily used as a biomarker to detect or track ovarian cancer and sometimes other cancers like pancreatic or lung cancer. It can also help assess the spread of cancer or monitor treatment effectiveness in some cases. However, it is not a definitive test for cancer diagnosis alone.
Why Might You Need This Test?
Your doctor may order a CA-125 test if you have symptoms like abdominal pain, bloating, or unexplained weight loss, or if you have a known history of ovarian cancer or other related conditions. It may also be used during follow-up for cancer patients to check for recurrence.
How Is the Test Performed?
A blood sample is taken from a vein in your arm. The sample is then sent to a lab for analysis using an immunoassay method to detect and measure the CA-125 protein levels in your serum or plasma.
What Do Your Results Mean?
Elevated CA-125 levels may suggest the presence of ovarian cancer or other malignancies, but they can also be raised in other conditions like endometriosis or benign ovarian cysts. Results should always be interpreted by your healthcare provider in the context of your medical history and symptoms.
Reference range
Reference values vary by laboratory; consult the performing laboratory's reference range. Generally, elevated CA 50 levels (>25 U/mL) may suggest malignancy, particularly of the gastrointestinal tract.N/A
No special preparation required. Specimen collection is not affected by fasting status.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
◆Associated findings1
Short name
CA-125 Fluid
Frequently asked questions
What causes CA-125 levels to be higher than usual?
Can CA-125 levels be affected by medications?
How often should I get this test if I have a history of cancer?
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