Version July 2025
Please read the Disclaimer at the end of this page.
What is a CA 125 test? —
This is a type of blood test. It measures the level of CA 125 in the blood.
CA 125 is a protein in the blood. Different things can affect a person's CA 125 level, including:
●Cancer – The CA 125 level can go up when a person has ovarian cancer. Other types of cancer can also cause the level to go up.
●Other health conditions – Other conditions besides cancer can also cause the CA 125 level to go up. These include ovarian cysts, fibroids (growths in the uterus), and endometriosis (when cells normally found in the uterus grow outside the uterus).
●Other things — A person's CA 125 level can also be affected by their age, weight, and menstrual cycle, and whether they smoke.
Why might I get a CA 125 test? —
Your doctor or nurse might want you to have a CA 125 test to:
●"Screen" for ovarian cancer – Screening is a way for doctors to look for early signs of ovarian cancer in some people who are at high risk but have no symptoms. However, CA-125 is not a good screening test, and some doctors do not use it in this situation. There is no role for screening in people who are not at high risk.
●Help figure out if a mass on the ovary is cancer
●See how treatment for ovarian cancer is working, or see if ovarian cancer comes back
How do I prepare for a CA 125 test? —
You need to get a "blood draw." Your doctor or nurse will tell you where to go for this.
It might help to wear a short-sleeve shirt to your blood draw appointment. This makes it easier for the person drawing your blood to get to your arm.
What happens during a blood draw? —
A needle is used to take a small amount of blood from your arm (figure 1). Collecting the blood only takes a few minutes. The blood is then tested in a lab.
Tell the person who takes your blood:
●If you take "blood thinner" medicines or if you have a bleeding problem – They will make sure your bleeding is under control before you leave.
●If you have a latex allergy – Some of the supplies used for blood draws might contain latex.
●If you have a preferred arm to use
Most of the time, getting blood taken does not cause problems. You might have a little soreness or bruising where the needle went in.
What do my results mean? —
Your doctor or nurse will tell you when to expect your results, and will contact you with the results. Or if you use an online "patient portal," you might get an alert there when your results are ready.
If the results show your CA 125 level is high, your doctor or nurse will talk to you about what to do next. They might need to do more tests to figure out the cause.
If you do have a health problem, your doctor will work with you to come up with a plan for treatment.
Patient education: Ovarian cancer screening (The Basics)
Patient education: Ovarian cancer (The Basics)
Patient education: Ovarian cysts (The Basics)
Patient education: Uterine fibroids (The Basics)
Patient education: Endometriosis (The Basics)
Patient education: Screening for ovarian cancer (Beyond the Basics)
Patient education: Ovarian cancer diagnosis and staging (Beyond the Basics)
Patient education: Treatment of ovarian cancer (Beyond the Basics)
Patient education: Ovarian cysts (Beyond the Basics)
Patient education: Uterine fibroids (Beyond the Basics)
Patient education: Endometriosis (Beyond the Basics)
