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Cancer Antigen 125 (CA-125) with Plasma Specimen, Confirmation Test

Published: August 9, 2026Updated: August 17, 2026

This test measures the level of CA-125, a protein sometimes produced by certain types of ovarian cancer and other conditions affecting the ovaries, fallopian tubes, or peritoneum. It helps doctors assess risk, monitor treatment response, or detect recurrence in these conditions.

Quick summary

["CA-125 levels may indicate ovarian cancer or other related health issues, guiding treatment decisions or follow-up care."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 17, 2026Editorial policy

Key facts at a glance

LOINC
19190-8
Short code
CA549PF
Synonyms
Cancer Ag549 Plr-aCnc
Category
chemistry
Sample
fluid
Container
Sterile, leak-proof pleural fluid collection container; sterile red-top or SST tube for transport to laboratory
Units
N/A
Critical range
0.5 N/A – —
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
Immunoassay (typically chemiluminescent or electrochemiluminescent immunoassay)
CPT
86316
SNOMED
395794004
Specimen volume
5-10 mL of pleural fluid; minimum 2 mL required for analysis
Stability
Refrigerated (2-8°C): up to 7 days; Frozen (-20°C or below): up to 3 months. Avoid repeated freeze-thaw cycles.
Hemolysis max
300
TAT
24–72 hours
Order
routine

Why This Test Might Be Ordered

Your doctor may recommend this test if you have symptoms like persistent abdominal pain, bloating, or unusual vaginal bleeding. It’s also used during screening for ovarian cancer in high-risk individuals or after treatment to check for recurrence. Sometimes, it’s part of a routine follow-up for known ovarian cancer patients.

What to Expect Before the Test

No special preparation is needed, but you may be asked to fast for 8–12 hours before drawing blood. Wear comfortable clothing and plan to stay for about 15 minutes while the blood is drawn. If you’re on blood thinners, let your doctor know before the test.

What Happens During the Test

A healthcare professional will insert a needle into a vein in your arm to collect a small amount of blood. You may feel a slight pinch, but it usually doesn’t cause discomfort. The blood is then sent to a lab for analysis using an immunoassay method to detect CA-125 levels.

What the Results Mean

Results are compared to a reference range, but exact values can vary by lab. High levels may suggest ovarian cancer or other conditions affecting the ovaries, while low levels may indicate no active cancer. Your doctor will interpret results in the context of your medical history and symptoms.

Reference range

CA 549 is not typically elevated in benign pleural effusions. Elevated levels in pleural fluid are suggestive of metastatic breast or ovarian carcinoma. Reference values are not well established; results should be interpreted in conjunction with clinical findings, cytology, and comparison with serum levels.N/A

Specimen: fluid

No special patient preparation required. Thoracentesis is performed by qualified personnel under sterile conditions, typically with local anesthesia.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

CA-125 is a biomarker often used in ovarian cancer diagnosis, staging, and monitoring. While it’s not specific to cancer alone (false positives can occur in other conditions like endometriosis or pelvic inflammation), it remains valuable in guiding treatment plans and detecting recurrence. Always discuss results with your healthcare provider.

Short name

CA-125 Confirmation

Frequently asked questions

How Often Will I Need This Test?
The frequency depends on your medical situation. For ovarian cancer patients, it may be ordered every few months during treatment or after surgery to check for recurrence. High-risk individuals might have screening tests more regularly. Follow your doctor’s recommendations.
Can I Avoid This Test If I Feel Well?
Not necessarily. Even if you feel fine, your doctor may order this test to monitor a known condition, screen for risk, or check for early signs of recurrence. It’s important to follow up as scheduled, even without symptoms.
What If My Results Are Abnormal?
If your CA-125 levels are elevated, your doctor may recommend further testing, such as imaging scans or additional blood tests, to investigate the cause. They’ll work with you to determine the next steps based on your overall health and symptoms.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

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.

Medical Disclaimer

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