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Ovarian Cancer Antigen 125 (CA-125), Serum/Plasma

Published: August 9, 2026Updated: August 16, 2026

CA-125 is a blood test that may help evaluate ovarian cancer and can also help monitor treatment or recurrence.

Quick summary

["An elevated CA-125 can occur with ovarian cancer, but it can also result from noncancerous conditions."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
11658-2
Short code
Ovarian a-L Vmin dias DOP
Synonyms
Ovarian a-L Vmin dias DOP
Category
liver
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
us-doppler
CPT
86038
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

What is this test?

CA-125 is a protein that some cells in the body, including certain ovarian cells, can produce. A blood sample is measured for CA-125 to help evaluate possible ovarian cancer and to monitor people with a known diagnosis.

Why might I need this test?

Your clinician may order CA-125 when symptoms or imaging suggest a possible ovarian mass or when you have a higher risk of ovarian cancer. It may also be used to check treatment response or look for signs that cancer has returned.

How is the test performed?

A small blood sample is drawn from a vein in your arm and sent to a laboratory for analysis. The result is usually reported as a concentration, with the laboratory providing its own reference range.

How do I prepare for the test?

CA-125 usually requires no special preparation. Follow any instructions from your clinician, and tell the laboratory if you are pregnant because pregnancy can affect the result.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

A high CA-125 level may occur with ovarian cancer and certain other cancers, but it is not specific for cancer. Endometriosis, pelvic inflammation, pregnancy, and some other noncancerous conditions can also raise the level. Your clinician will interpret the result along with your symptoms, imaging, examination, and medical history.

Short name

CA-125

Frequently asked questions

Does an elevated CA-125 level mean I have ovarian cancer?
No. CA-125 can be elevated for many noncancerous reasons, so an abnormal result alone cannot diagnose ovarian cancer. Additional evaluation may be needed.
Is CA-125 a screening test for everyone?
CA-125 is not recommended as a general screening test for all average-risk people because abnormal results are common and may lead to unnecessary testing. It may be used in selected people with a higher risk or possible ovarian cancer.
How is CA-125 used after an ovarian cancer diagnosis?
The test may be used alongside imaging and symptoms to assess treatment response or monitor for recurrence. A change in the CA-125 level is interpreted by your oncology care team.
  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 16, 2026. · Read our editorial policy