CA-125
| Clinical | Optimal | |
|---|---|---|
| Male | N/A | Not routinely tested in men |
| Female | 0 - 35 kU/L | <35 kU/L |
What is CA-125?
CA-125 (Cancer Antigen 125) is a glycoprotein found on the surface of many cell types, particularly those lining the reproductive tract, peritoneum (abdominal cavity lining), and pleura (lung lining). It is released into the bloodstream and can be measured as a tumour marker.
CA-125 is primarily used in the monitoring of ovarian cancer, where it helps assess treatment response and detect recurrence. It is also used alongside ultrasound in the Risk of Malignancy Index (RMI) to evaluate pelvic masses found on imaging.
Importantly, CA-125 is not a reliable screening test for ovarian cancer in the general population because it can be elevated in many benign conditions. Large clinical trials have shown that population-wide CA-125 screening does not significantly reduce ovarian cancer mortality.
Why CA-125 Matters for Your Health
Ovarian cancer is the sixth most common cancer in women in the UK and is often diagnosed at an advanced stage because early symptoms are vague and non-specific. While CA-125 alone is not sensitive or specific enough for population screening, it plays an important role in the clinical pathway for women presenting with suspicious symptoms.
For women being monitored after ovarian cancer treatment, serial CA-125 measurements are a cornerstone of follow-up care. Rising levels often precede clinical or imaging evidence of recurrence by several months.
In the context of preventive health, CA-125 can form part of a broader health assessment, particularly for women with a family history of ovarian or breast cancer. However, results must be interpreted carefully in the context of clinical findings and other investigations.
CA-125& Your Wearable Data
CA-125 is a tumour marker primarily used for monitoring ovarian cancer treatment and detecting recurrence. It is not recommended for general screening due to frequent false positives from benign conditions including endometriosis, fibroids, pelvic inflammatory disease, and even menstruation. Results should always be interpreted in clinical context.
While wearable devices cannot predict or monitor CA-125 levels, general health monitoring through your wearable supports comprehensive health awareness. For women with known ovarian conditions, wearable cycle tracking and symptom monitoring provide continuous data between clinical assessments, helping detect changes that may warrant earlier investigation including CA-125 testing.
What High CA-125 May Suggest
Elevated CA-125 may suggest ovarian cancer, but many benign conditions also cause elevation. Common non-cancerous causes include endometriosis, ovarian cysts, pelvic inflammatory disease, uterine fibroids, menstruation, pregnancy, liver cirrhosis, and pleural effusions.
The degree of elevation can provide some guidance: levels above 200 kU/L in postmenopausal women with a pelvic mass are highly suspicious for malignancy, while modest elevations (35–100 kU/L) in premenopausal women are more commonly associated with benign conditions.
If results suggest elevated CA-125, your GP will typically arrange a pelvic ultrasound and may refer to gynaecology for further assessment. The clinical context, including menopausal status, symptoms, and imaging findings, is essential for appropriate interpretation.
What Low CA-125 May Suggest
Low or normal CA-125 levels are generally reassuring, particularly in postmenopausal women. However, a normal CA-125 does not exclude ovarian cancer, as early-stage disease and certain ovarian cancer subtypes (such as mucinous tumours) may not produce elevated CA-125.
In women being monitored after ovarian cancer treatment, sustained low CA-125 levels are a positive prognostic sign. A return to normal levels following treatment suggests a good response.
Normal CA-125 levels do not require any specific follow-up in the general population.
How to Optimise Your CA-125
Food
Support reproductive and general health with an anti-inflammatory, nutrient-dense diet. Include cruciferous vegetables (broccoli, cauliflower, kale) for their cancer-protective compounds. Consume diverse colourful vegetables and fruits for antioxidant protection. Include omega-3 fatty acids from oily fish to support anti-inflammatory pathways. Ensure adequate dietary fibre intake for hormonal balance and toxin clearance. Green tea contains EGCG, a polyphenol with demonstrated anti-cancer properties in laboratory research.
Lifestyle
Maintain a healthy body weight, as obesity is associated with increased ovarian cancer risk. Engage in regular physical activity, which has been linked to reduced risk of several gynaecological cancers. Avoid smoking and limit alcohol consumption. Be aware of persistent symptoms that may indicate ovarian cancer: bloating, pelvic pain, difficulty eating or feeling full quickly, and urinary symptoms. Report these to your GP if they occur on most days for three weeks or more. Use of the combined oral contraceptive pill has been associated with reduced ovarian cancer risk, though this should be discussed with your GP.
Supplements
Vitamin D3 supplementation may support overall cancer risk reduction, particularly given the high prevalence of deficiency in the UK. Omega-3 fatty acids from fish oil support anti-inflammatory pathways. Green tea extract (EGCG) has laboratory evidence for supporting healthy cell division, though clinical evidence is still emerging.
When to Speak to Your GP
See your GP if CA-125 is elevated above 35 kU/L, particularly if you are postmenopausal or experiencing persistent symptoms such as bloating, pelvic or abdominal pain, difficulty eating, or urinary changes. Women with a family history of ovarian or breast cancer (particularly BRCA1/BRCA2 mutations) should discuss enhanced surveillance with their GP or genetic counsellor. Rising CA-125 in women with a cancer history requires urgent specialist review.
References
- NHS. Ovarian cancer — Diagnosis. Updated 2024. nhs.uk
- NICE. Ovarian cancer: recognition and initial management. NG122. nice.org.uk
- Lancet. Jacobs IJ, et al. Ovarian cancer screening and mortality in the UK Collaborative Trial of Ovarian Cancer Screening (UKCTOCS). Lancet. 2016;387(10022):945-956. pubmed.ncbi.nlm.nih.gov
- BMJ. Menon U, et al. Ovarian cancer population screening and mortality after long-term follow-up in the UK CTOCS. Lancet. 2021;397(10290):2182-2193. pubmed.ncbi.nlm.nih.gov
Medical Disclaimer— This content is for general educational and informational purposes only. It does not constitute medical advice, diagnosis, or treatment. Omniwo Ltd is a wellness information service and is not a medical device, clinical laboratory, or regulated healthcare provider under MHRA guidelines. The “optimal ranges” presented on this page are based on published clinical guidelines (WHO, NICE, NHS) and peer-reviewed research; they represent functional wellness targets and may differ from standard laboratory reference ranges. Individual results should always be interpreted by a qualified healthcare professional (such as your GP) who understands your full medical history. Do not start, stop, or change any medication or supplement based solely on this information. If you are experiencing symptoms, seek medical attention promptly.