‎What is a CA125 blood test?

This leaflet will give you information about the CA125 blood test. You may be feeling unwell or perhaps you have spoken to your GP about symptoms. To help find out what is wrong your GP has suggested that you have a CA125 blood test. Your GP may advise you not to have the test immediately before or during your period as it can interfere with the result. If you have further questions after reading this information you should speak to your GP.

CA125 is a protein that is found in blood. A small sample of blood will be taken from your arm and sent to a lab where a simple test will measure the level of CA125 in your blood sample. In most healthy women the level of CA125 is usually less than 35. However, some women do have a naturally high level of CA125 in their blood. The level of CA125 in the blood can rise for many reasons which include endometriosis, menstruation, ovarian cysts and, sometimes, ovarian cancer.

Why has my GP asked me to have a CA125 blood test?

Symptoms including bloating, tummy pain, difficulty eating or feeling full and needing to wee more often or urgently can sometimes be caused by ovarian cancer. It is very unlikely that you will have ovarian cancer, but your GP will want to rule out the possibility. The CA125 test is a useful way for your GP to gather some more information and will help your GP decide what to do next.

Does a CA125 result above 35 mean I have ovarian cancer?

No. The level of CA125 in your blood can increase for other reasons. A CA125 blood test result above 35 is not in itself a diagnosis of ovarian cancer. If the level of CA125 in your blood is 35 or higher, your GP should arrange for you to have an ultrasound scan of your tummy and pelvis. The ultrasound scans will create pictures of your ovaries so that they can be checked for anything unusual, and will help your GP gather more information.

Does a CA125 result below 35 mean that I don’t have ovarian cancer?

Most women with a result below 35 will not have ovarian cancer. However, a small number of women with ovarian cancer will have a CA125 test result below 35. If your symptoms continue or worsen then you must go back to your GP and let them know; make an appointment for a check-up within one month.

Next steps

Getting your test result - your GP will let you know how long your test result should take to come back from the lab; they will also tell you how to find out the result of your test. However, if you don’t hear anything within a couple of weeks, give your GP a call - sometimes results get lost. If you received your test results and you are not sure what they mean go back to your GP and ask for clarification. If your test result is above 35 your GP will arrange further tests or a follow-up appointment.

Note down your symptoms - if your CA125 level is below 35, but your symptoms continue or worsen then you must go back to your GP within a month and let them know. Why not keep a symptoms diary; each day make a quick note of each symptom and how bad it is? This might help your GP identify the cause of your symptoms.

Content used with permission from the Target Ovarian Cancer website: CA125 blood test. Copyright for this leaflet is with Target Ovarian Cancer.