{"id":"ca-15-3","name":"CA 15-3 (Cancer Antigen 15-3)","shortName":"CA 15-3","aliases":["CA 15-3","CA15-3","Cancer Antigen 15-3","MUC1 (CA 15-3)","Cancer Antigen (CA) 15-3","CA 15.3","CA-15-3","Cancer Ag 15-3","Cancer Antigen-Breast (CA 15-3)"],"abbreviations":["CA 15-3","CA15-3"],"loinc":[{"code":"6875-9","primary":true},{"code":"83083-6","primary":false}],"specimen":"serum","units":[{"ucum":"U/mL","display":"U/mL"},{"ucum":"kU/L","display":"kU/L"}],"referenceRanges":[{"population":"Adults","low":0,"high":30,"unit":"U/mL","unitDisplay":"U/mL","note":"Labs print different limits for this test: Mayo Clinic Laboratories under 30 U/mL, ARUP 0 to 31, Quest under 32 and Labcorp 0.0 to 25.0, even though Labcorp, Mayo and ARUP all use an electrochemiluminescence method. We use 30 U/mL, which sits in the middle of that spread. CA 15-3 limits depend on the assay, so use the range printed on the lab report.","sources":[{"title":"CA153 - Overview: Cancer Antigen 15-3 (CA 15-3), Serum","url":"https://www.mayocliniclabs.com/test-catalog/overview/81607","publisher":"Mayo Clinic Laboratories"},{"title":"Cancer Antigen-Breast (CA 15-3), test 0080464","url":"https://ltd.aruplab.com/Tests/Pub/0080464","publisher":"ARUP Laboratories"},{"title":"CA 15-3 (test code 5819)","url":"https://testdirectory.questdiagnostics.com/test/test-detail/5819/ca-15-3?cc=MASTER","publisher":"Quest Diagnostics"},{"title":"Cancer Antigen (CA) 15-3 (test 143404)","url":"https://www.labcorp.com/tests/143404/cancer-antigen-ca-15-3","publisher":"Labcorp"}]}],"review":{"status":"ai-verified","label":"AI-verified against cited sources. Awaiting expert review","lastReviewed":"2026-10-03"},"summary":"A protein on breast and other gland cells. Doctors use it to follow breast cancer treatment, and many harmless conditions can raise it too.","url":"https://bloodtesttracker.com/markers/ca-15-3","notice":"Information, not medical advice. Ranges differ between labs, so the range on your own report is the one your result is judged against."}