{"id":"protein-s-activity","name":"Protein S Activity","shortName":"Protein S Activity","aliases":["Protein S, Functional","Protein S Activity (Clotting)","Protein S Activity Assay","Protein S Func","Protein S Functional","Functional Protein S","Protein S Activity, P","Protein S Activity, Plasma","Protein S Clottable","PROT S F"],"abbreviations":["PS Activity"],"loinc":[{"code":"27822-6","primary":true},{"code":"31102-7","primary":false},{"code":"5892-5","primary":false}],"specimen":"plasma","units":[{"ucum":"%","display":"%"},{"ucum":"[IU]/dL","display":"IU/dL"}],"referenceRanges":[{"population":"Men, 18+","low":66,"high":143,"unit":"%","unitDisplay":"%","note":"ARUP Laboratories interval for males 18 and over (clot-based method). Mayo Clinic Laboratories lists 65–150% for men, 50–150% for women under 50 and 65–150% for women 50 and over. A UK haemostasis reference quotes above 70–140 U/dL for men, and Indiana University Health lists 52–136% for both sexes. Ranges depend on the method, so use the range printed on your own report.","sources":[{"title":"Protein S, Functional (test 0030114)","url":"https://ltd.aruplab.com/Tests/Pub/0030114","publisher":"ARUP Laboratories"},{"title":"Protein S Activity, Plasma (test ID SFX)","url":"https://www.testcatalog.org/show/SFX","publisher":"Mayo Clinic Laboratories (Extended Catalog, via testcatalog.org)"},{"title":"Protein S Assays","url":"https://www.practical-haemostasis.com/Thromobophilia/ps_assays.html","publisher":"Practical-Haemostasis.com"},{"title":"Thrombosis & Hemostasis Reference Ranges (updated 1/11/2021)","url":"https://cdn.iuhealth.org/resources/Thrombosis-Hemostasis-Ref-Ranges-No-StarMax.pdf","publisher":"Indiana University Health Pathology Laboratory","year":2021}]},{"population":"Women, 18+","low":57,"high":131,"unit":"%","unitDisplay":"%","note":"ARUP Laboratories interval for females 18 and over (clot-based method). Mayo Clinic Laboratories splits women by age: 50–150% under 50 and 65–150% at 50 and over. A UK haemostasis reference quotes above 60–130 U/dL for women, and Indiana University Health lists 52–136% for both sexes. Pregnancy and estrogen-containing medicines lower protein S, and the ranges above are for people who are not pregnant. Use the range printed on your own report.","sources":[{"title":"Protein S, Functional (test 0030114)","url":"https://ltd.aruplab.com/Tests/Pub/0030114","publisher":"ARUP Laboratories"},{"title":"Protein S Activity, Plasma (test ID SFX)","url":"https://www.testcatalog.org/show/SFX","publisher":"Mayo Clinic Laboratories (Extended Catalog, via testcatalog.org)"},{"title":"Protein S Assays","url":"https://www.practical-haemostasis.com/Thromobophilia/ps_assays.html","publisher":"Practical-Haemostasis.com"},{"title":"Thrombosis & Hemostasis Reference Ranges (updated 1/11/2021)","url":"https://cdn.iuhealth.org/resources/Thrombosis-Hemostasis-Ref-Ranges-No-StarMax.pdf","publisher":"Indiana University Health Pathology Laboratory","year":2021}]}],"review":{"status":"ai-verified","label":"AI-verified against cited sources. Awaiting expert review","lastReviewed":"2026-10-03"},"summary":"Measures how well protein S works. Protein S is a natural blood thinner that helps protein C keep your blood from clotting too easily.","url":"https://bloodtesttracker.com/markers/protein-s-activity","notice":"Information, not medical advice. Ranges differ between labs, so the range on your own report is the one your result is judged against."}