Blood test

Normal CA 125 (Carcinoma Antigen) in a blood test

Blood test
Normal CA 125 (Carcinoma Antigen) in a blood test
Last update: 27/10/2021

What is the normal value of CA 125 (Carcinoma Antigen) in a blood test?

The normal range of the CA 125 (Carcinoma Antigen) is expressed in U/ml.

Women: < 35 U/ml

Why normal values can differ across different labs?

Each laboratory must establish its own normal range for the CA 125 (Carcinoma Antigen) in a blood test. These ranges depend on the makeup of the local population, the technologies used and the accuracy of the measurement. There may be also slight differences in the normal levels according to age, gender, race or ethnic origin, geographic region, diet, type of sample and other relevant status.

Your doctor will study the results along with your medical record, screenings, physical condition, symptoms and any other relevant information about your situation.

Besides, in the first trimester of pregnancy the CA-125 level may be increased considerably.

What does CA 125 (Carcinoma Antigen) mean?

Cancer Antigen 125 (CA-125) is a glycoprotein with a high molecular weight (> 200kDa). The physiological function of CA 125 is still unknown.

There is an increase in the CA-125 antigen in ovarian neoplasm and other female pathologies related to paramesonephric ducts (Fallopian tubes, uterus, cervix).

    What is the CA 125 (Carcinoma Antigen) test used for?

    The CA 125 (carcinoma antigen) is a tumor marker. It means that it raises in the presence of a malignant tumor. CA 125 is most useful as a marker for ovarian cancer. It means that there is an increase in CA 125 antigen in the blood in case of suffering from ovarian cancer.

    However, CA 125 antigen is not specific enough to be used to screen healthy clients for ovarian cancer because the elevation of CA 125 may be seen in a number of non ovarian carcinomas, including endometrial, pancreatic, lung, breast, colorectal, and other gastrointestinal tumors. It is also elevated in patients with benign conditions, such as cirrhosis, endometriosis, pericarditis, and early pregnancy.

    The test is usually performed in women at high risk for this disease because of a history of ovarian cancer in the family or women who have unexplained symptoms of bloating and pelvic or abdominal pain.

    CA 125 is not very sensitive for ovarian cancer. It is only elevated in 50% of patients with stage I disease, 90% with stage II, and more than 90% with stages III and IV.

    CA 125 is also useful in differentiating ovarian cancer from benign diseases (endometriosis, pelvic inflammatory disease, etc.) in patients with palpable ovarian masses. For this matter, it is used together with the CEA tumor marker. When the CA-125/CEA ratio is high the probability of suffering from ovarian cancer is very high. For example, for a ratio greater than 25 more than 80% of the patients will have an ovarian cancer.

    Where can I find more information about CA 125 (Carcinoma Antigen) in a blood test?

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    Which values are considered a normal CA 125 (Carcinoma Antigen) in a blood test?

    The following values are considered to be normal values:

    IMPORTANT: These levels are expressed in U/ml. They are an example of a healthy woman of about 40 years old with no known disease and not taking any medication. The ranges can be different depending on the laboratory or on your personal circumstances.

    CA 125
    0 U/mL1 U/mL2 U/mL3 U/mL4 U/mL5 U/mL6 U/mL7 U/mL
    8 U/mL9 U/mL10 U/mL11 U/mL12 U/mL13 U/mL14 U/mL15 U/mL
    16 U/mL17 U/mL18 U/mL19 U/mL20 U/mL21 U/mL22 U/mL23 U/mL
    24 U/mL25 U/mL26 U/mL27 U/mL28 U/mL29 U/mL30 U/mL31 U/mL
    32 U/mL33 U/mL34 U/mL35 U/mL    
    Medically reviewed by our Medical staff on 27/10/2021


    • Concise Book of Medical Laboratory Technology: Methods and Interpretations. 2nd Edition. 2015. Ramnik Sood. ISBN: 978-93-5152-333-8. Pag. 685.
    • Laboratory tests and diagnostic procedures : with nursing diagnoses. Jane Vincent Corbett, Angela Denise Banks. 8th ed. 2013. ISBN: 978-0-13-237332-6. Pag. 248.
    • Tietz. Fundamentals of Clinical Chemistry. Carl A. Burtis, Edward R. Ashwood, David e. Bruns. 6th edition. 2008. Pag 354. ISBN: 978-0-7216-3865-2.

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