CA-125 blood test
Ovarian cancer - CA-125 test
The CA-125 blood test measures the level of the protein CA-125 in the blood.
Blood is drawn from a vein (venipuncture), usually from the inside of the elbow or the back of the hand. A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. Preparation may vary depending on the specific test.
Ovarian cancer is particularly dangerous because its presence is difficult to detect until it has spread beyond the ovaries.
How the Test is Performed
A blood sample is needed.
How to Prepare for the Test
No preparation is necessary.
How the Test will Feel
When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or a slight bruise. This soon goes away.
Why the Test is Performed
CA-125 is a protein that is found more in ovarian cancer cells than in other cells.
This blood test is often used to monitor women who have been diagnosed with ovarian cancer. The test is useful if the CA-125 level was high when the cancer was first diagnosed. In these cases, measuring the CA-125 over time is a good tool to determine if ovarian cancer treatment is working.
The CA-125 test may also be done if a woman has symptoms or findings on ultrasound that suggest ovarian cancer.
In general, this test is not used to screen healthy women for ovarian cancer when a diagnosis has not yet been made.
Normal Results
A level above 35 units/milliliter (U/mL) is considered abnormal.
Normal value ranges may vary slightly among different lab. Some labs use different measurements or test different samples. Talk to your health care provider about the meaning of your specific test results.
What Abnormal Results Mean
In a woman who has ovarian cancer, a rise in CA-125 usually means that the disease has progressed or come back (recurred). A decrease in CA-125 usually means the disease is responding to current treatment.
In a woman who has not been diagnosed with ovarian cancer, a high CA-125 level may mean a number of things. While it may mean that she has ovarian cancer, it can also indicate other types of cancer, as well as several other diseases, such as endometriosis, which are not cancer.
In healthy women, an elevated CA-125 usually does not mean ovarian cancer is present. Most healthy women with an elevated CA-125 do not have ovarian cancer, or any other cancer.
Any woman with an abnormal CA-125 test needs further tests. Sometimes surgery is needed to confirm the cause.
Risks
There is little risk involved with having your blood taken. Veins and arteries vary in size from one person to another and from one side of the body to the other. Taking a blood sample from some people may be more difficult than from others.
Other risks associated with having blood drawn are slight, but may include:
- Fainting or feeling lightheaded
- Multiple punctures to locate veins
- Hematoma (blood accumulating under the skin)
- Excessive bleeding
- Infection (a slight risk any time the skin is broken)
References
Coleman RL, Liu J, Matsuo K, Thaker PH, Westin SN, Sood AK. Carcinoma of the ovaries and fallopian tubes. In: Niederhuber JE, Armitage JO, Kastan MB, Doroshow JH, Tepper JE, eds. Abeloff's Clinical Oncology. 6th ed. Philadelphia, PA: Elsevier; 2020:chap 86.
Freund KM. Approach to women's health. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 219.
Thomson C. Ovarian neoplasms. In: Layden EA, Thomson A, Owen P, Madhra M, Magowan BA, eds. Clinical Obstetrics and Gynaecology. 5th ed. Philadelphia, PA: Elsevier; 2023:chap 12.
Version Info
Version: 2.0
Last reviewed on: 10/14/2024
Reviewed by: Warren Brenner, MD, Oncologist, Lynn Cancer Institute, Boca Raton, FL. Review provided by VeriMed Healthcare Network. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.
