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CA-125 test

Also called: Cancer antigen 125

CA-125 is a protein that can be high in ovarian cancer. It's mainly used to follow treatment, not to screen.

SampleA small tube of blood from a vein in your arm
Fasting?Usually not needed
ResultsSeveral days
Good to knowOne result rarely tells the whole story. Your provider looks at your results together with your symptoms, exam, and other tests.

What the test is

Many harmless conditions raise it, like periods, endometriosis, fibroids, and pregnancy.

Why it's done

  • Following ovarian cancer
  • A pelvic mass, especially after menopause

Getting ready and what happens

  • No preparation is needed.

How the test is done

  • A health worker cleans the skin, puts a band around your arm, and draws blood from a vein with a small needle. It takes a few minutes.

What the results mean

ResultTypical range for adults
CA-125Below about 35 U/mL

Normal ranges vary from lab to lab and can differ by age, sex, and pregnancy. Your report lists your lab's own range next to each result. A result a little outside the range is often not a problem.

High

Doesn't diagnose cancer on its own; imaging and specialist review are needed.

Questions to ask your provider

  • What do my results mean for me?
  • Do I need to repeat this test or have other tests?

Risks

A blood draw is very safe. You may have slight pain or a small bruise where the needle went in.

Related conditions

Sources

Last updated 2026-11-13.