CA-125
Also known as: Cancer Antigen 125
What Does CA-125 Measure?
CA-125 (Cancer Antigen 125) is a protein found on the surface of many ovarian cancer cells and some normal tissues. A blood test measures the level of this protein circulating in the bloodstream. The test detects how much of this antigen is present, typically expressed in units per milliliter (U/mL). Elevated levels can indicate the presence of certain cancers, particularly ovarian cancer, as well as various non-cancerous conditions that cause inflammation or tissue irritation.
Why Does CA-125 Matter?
CA-125 is primarily used as a tumor marker to monitor the progression or recurrence of ovarian cancer in women who have already been diagnosed. It is a valuable tool for assessing how well treatment is working — falling levels generally indicate a positive response to therapy, while rising levels may signal recurrence. Although it is not reliable enough as a standalone screening test for ovarian cancer in the general population due to its limited specificity, it plays a critical role in guiding clinical decisions when combined with imaging studies and other diagnostic tools. It can also be elevated in endometriosis, uterine fibroids, pelvic inflammatory disease, and other gynecological conditions.
Normal Ranges
Males
Less than 35 U/mL
Females
Less than 35 U/mL (postmenopausal); may be slightly higher in premenopausal women due to menstruation or benign gynecological conditions
Children
Varies by age; CA-125 testing is rarely performed in children and reference ranges are not well established
Causes of High Levels
- Ovarian cancer or other gynecological cancers (endometrial, cervical, fallopian tube)
- Endometriosis — tissue similar to the uterine lining growing outside the uterus
- Uterine fibroids (leiomyomas) — noncancerous growths in the uterus
- Pelvic inflammatory disease (PID) or other pelvic infections
- Liver disease including cirrhosis, hepatitis, or liver failure
- Other cancers such as pancreatic, lung, breast, or colon cancer
- Pregnancy, especially in the first trimester
- Menstruation — normal menstrual cycle can transiently elevate CA-125
Causes of Low Levels
- Successful treatment of ovarian cancer (chemotherapy, surgery) leading to reduced tumor burden
How to Improve Your CA-125
Diet
- Consume a Mediterranean-style diet rich in fruits, vegetables, whole grains, and healthy fats to reduce systemic inflammation
- Increase intake of cruciferous vegetables (broccoli, cauliflower, kale) which contain compounds like sulforaphane that may support cancer prevention
- Limit processed foods, red meat, and refined sugars that can promote inflammation
- Include omega-3-rich foods such as fatty fish (salmon, mackerel), flaxseeds, and walnuts to help modulate inflammatory pathways
- Stay well-hydrated and limit alcohol consumption, as excessive alcohol can impair liver function and elevate CA-125
Supplements
- Vitamin D3 (1,000–2,000 IU/day) — low vitamin D levels have been associated with increased cancer risk; consult your doctor before supplementing
- Omega-3 fatty acids (1–3 g/day of EPA+DHA) — may help reduce inflammation linked to elevated CA-125
- Curcumin/turmeric extract (500–1,000 mg/day with piperine for absorption) — has demonstrated anti-inflammatory and potential anti-cancer properties in research studies
- Green tea extract (EGCG, 400–800 mg/day) — contains polyphenols with antioxidant and anti-inflammatory effects; consult a physician if on medications
Related Biomarkers
Frequently Asked Questions
Does a high CA-125 level mean I have ovarian cancer?
Not necessarily. While elevated CA-125 is associated with ovarian cancer, it can also be raised by many non-cancerous conditions including endometriosis, uterine fibroids, pelvic inflammatory disease, liver disease, pregnancy, and even menstruation. CA-125 is not specific enough to diagnose ovarian cancer on its own. A high result should always be evaluated by a physician alongside imaging studies such as pelvic ultrasound, physical examination, and other clinical information before any conclusions are drawn.
Can CA-125 be used as a screening test for ovarian cancer?
CA-125 is not recommended as a routine screening test for ovarian cancer in the general population. Its relatively low specificity means that many women without cancer can have elevated levels, leading to unnecessary anxiety, further testing, and even invasive procedures. Major medical organizations, including the U.S. Preventive Services Task Force, do not recommend routine CA-125 screening in average-risk women. However, it may be used in surveillance for women with a known high risk (e.g., BRCA gene mutations) or for monitoring known ovarian cancer cases.
How is CA-125 used during ovarian cancer treatment?
In women diagnosed with ovarian cancer, CA-125 is a valuable tool for monitoring treatment response and detecting recurrence. Before treatment, a baseline CA-125 level is established. During chemotherapy or after surgery, declining CA-125 levels generally indicate that the treatment is effective and the tumor burden is decreasing. Conversely, a rising CA-125 level during follow-up can be an early warning sign of cancer recurrence, sometimes appearing months before symptoms develop or tumors are visible on imaging. Serial CA-125 measurements are typically performed every 3–6 months after treatment completion.