What is the Cancer Antigen 125 Test?

Cancer Antigen 125 (CA-125) is a glycoprotein produced by cells lining the ovaries, pelvis and abdomen. Elevated levels are most commonly associated with ovarian cancer, particularly epithelial ovarian cancer, but may also be seen in other pelvic or abdominal conditions.

The CA-125 blood test measures the concentration of this marker in the bloodstream. It is not used as a general screening test, but plays an important role in monitoring disease progression, response to treatment and recurrence in patients with known or suspected ovarian cancer.

Results are always interpreted in combination with imaging studies, clinical symptoms and other laboratory findings.

Why do I need a test for Cancer Antigen 125?

You may need this test if ovarian cancer is suspected, already diagnosed or being monitored after treatment. CA-125 is particularly useful for tracking changes over time rather than making a diagnosis from a single result.

The test is also used in the investigation of pelvic masses and unexplained abdominal symptoms, helping clinicians decide whether further imaging or specialist referral is required.

Symptoms and scenarios where testing is recommended:

• Suspected ovarian cancer
• Monitoring known ovarian malignancy
• Follow-up after ovarian cancer treatment
• Unexplained abdominal bloating or swelling
• Pelvic or lower abdominal pain
• Early satiety or appetite changes
• Monitoring response to chemotherapy or surgery
• Investigation of pelvic masses

Benefits of the CA-125 Test

• Key marker for ovarian cancer monitoring
  Widely used to track disease activity and progression.
• Assesses treatment response
  Falling levels often indicate effective therapy.
• Detects recurrence early
  Rising levels may signal relapse before symptoms appear.
• Supports clinical decision-making
  Helps guide imaging and treatment planning.
• Complements imaging studies
  Adds biochemical data alongside ultrasound or CT scans.
• Useful for long-term surveillance
  Enables trend analysis over time.
• Non-invasive monitoring tool
  Requires only a simple blood sample.
• Supports personalised cancer care
  Helps tailor follow-up and management strategies.

Step-by-Step: How Testing Works

Choose your preferred testing method

You can attend one of our UK partner clinics or arrange a home or hotel visit with a mobile phlebotomist.

Option 1 – In-Clinic Blood Draw

1. Select your nearest UK clinic and book an appointment.
2. A clinician or phlebotomist collects a venous blood sample.
3. The sample is analysed for CA-125 levels.
4. Results are delivered securely online.

Option 2 – Home or Hotel Phlebotomy (+£60)

1. Book a UK-wide home or hotel visit at a convenient time.
2. A trained phlebotomist collects your blood sample on-site.
3. The sample is packaged and transported to the laboratory.
4. Results are uploaded digitally without the need to travel.

Access your report

You can download and share your results with your GP or oncologist.

Your Results Explained

Low Levels

Low CA-125 levels are considered normal.
This suggests no biochemical evidence of active CA-125-producing tumour activity.
Typical UK reference range: usually <35 U/mL (ranges may vary by laboratory).

Normal Levels

Normal results indicate expected antigen levels in the bloodstream.
This reduces the likelihood of active ovarian cancer but does not completely exclude disease.

High Levels

Elevated CA-125 levels may indicate ovarian cancer or disease progression.
Levels can also rise in benign conditions such as endometriosis, fibroids or pelvic inflammation.
Results must always be interpreted alongside imaging and clinical findings.