Cancer Antigen 125 (CA-125) with Serum/plasma Measurement
This test measures levels of CA-125, a protein often produced by ovarian cancer cells and sometimes found in other conditions affecting the ovaries, uterus, or peritoneum. It is used to monitor treatment response or detect recurrence in patients with known ovarian cancer.
["CA-125 helps track ovarian cancer progression and response to treatment, though it’s not a definitive diagnostic test alone."]
Key facts at a glance
- LOINC
- 110107-0
- Short code
- CA125
- Synonyms
- Cancer Ag125 Msmt SerPl
- Category
- chemistry
- Sample
- serum
- Container
- Serum separator tube (SST) or red-top tube
- Units
- N/A
- Ref low
- 0
- Ref high
- 35
- Critical range
- 0.5 N/A – —
- Fasting
- false
- Population
- adult
- Sex
- female
- Age range
- 18–65 years
- Method
- Immunoassay (Chemiluminescent or Electrochemiluminescent)
- CPT
- 86304
- SNOMED
- 115341008
- Specimen volume
- 1 mL serum
- Stability
- Stable for 5 days at 2-8°C; for longer storage, freeze at -20°C or below
- Hemolysis max
- 100
- Lipemia max
- 100
- Icterus max
- 50
- TAT
- 4–24 hours
- Order
- routine
Why Is This Test Done?
Your doctor may order a CA-125 test if you have symptoms like abdominal pain, bloating, or irregular menstrual periods—especially if these are linked to ovarian or pelvic concerns. It’s also used to check for cancer spread or recurrence in people already diagnosed with ovarian cancer.
Who Might Need This Test?
Women at higher risk for ovarian cancer (due to family history, BRCA gene mutations, or other genetic factors) may receive regular CA-125 screenings. It’s also used in follow-up care for those with ovarian cancer or other related conditions.
What Does a High or Low Level Mean?
Elevated CA-125 levels can indicate ovarian cancer or other gynecological issues, but they’re not specific to cancer alone. Low levels may suggest no active cancer, but they don’t rule out other conditions. Your doctor will interpret results in context with your symptoms and medical history.
What to Expect During the Test
A blood sample is drawn from a vein in your arm. You may feel a slight pinch, but it’s quick and usually not painful. The blood is sent to a lab for analysis. Results are typically ready within a few days.
Reference range
<35 U/mL (commonly used clinical cutoff for adults)N/A
No special preparation required. CA-125 levels are not significantly affected by fasting. Sample may be collected at any time of day.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Clinical Significance: CA-125’s Role in Cancer Detection and Monitoring
Short name
CA-125 Screening/Confirmation Test
Frequently asked questions
How often will I need this test?
Can CA-125 test results be affected by other conditions?
What if my test results are abnormal?
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