CA125 is a protein measured in the blood that is often referred to as an "ovarian cancer marker". It has a genuine role in assessing certain symptoms and in monitoring, but it is widely misunderstood as a simple yes-or-no screening test. Understanding what it actually reflects helps make sense of a result — and explains why it is always interpreted alongside other information.
What CA125 is used for
CA125 can be raised when there is irritation or activity in the tissues lining the abdomen and pelvis. In practice, clinicians use it in a few defined ways:
- Assessing symptoms such as persistent bloating, pelvic or abdominal pain, or feeling full quickly — often alongside an ultrasound.
- Monitoring a known ovarian cancer during and after treatment, where changes over time are informative.
- Investigating a pelvic mass in combination with imaging and specialist review.
Why it is not a simple screening test
CA125 lacks the accuracy needed to screen women without symptoms. Its two limitations are important. First, it can be raised for many harmless reasons. Second, it can be normal even when ovarian cancer is present, particularly in early disease. Because of this, national screening programmes do not use CA125 for the general population.
Other reasons CA125 can be raised
A raised level is common and frequently unrelated to cancer. Benign causes include:
- Endometriosis and fibroids
- Ovarian cysts
- Menstruation and pregnancy
- Pelvic inflammation or infection
- Other conditions affecting the abdomen
Check CA125
A CA125 blood test used in assessing ovarian symptoms — best interpreted by a clinician alongside your history and, where appropriate, imaging.
Check CA125Making sense of your result
Because both raised and normal results can be misleading in isolation, CA125 should always be reviewed by a clinician who considers your symptoms, examination and any imaging. A single figure means little on its own; the trend over time and the overall clinical picture are what matter.
When to get checked
If you have persistent symptoms — bloating that does not settle, pelvic or abdominal pain, feeling full quickly or changes in appetite lasting more than a few weeks — see a clinician promptly. These symptoms usually have an innocent cause, but they should be assessed rather than ignored, and CA125 may form part of that assessment alongside examination and ultrasound.
Check CA125
Book online with OneMedicine — CQC-registered clinic in Birmingham, or a home visit / local clinic nationwide. Doctor-reviewed results, most within 24 hours.
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Specialist interest: Cardiovascular Medicine · OneMedicine, CQC-registered clinic