Test guide
Protein C and Protein S Tests
Protein C and protein S tests use a sample of your blood to measure how many of these proteins you have and how well they're working. Though they are often done together, these are separate tests. A protein C test measures protein C in your blood ; a protein S test measures protein S.
What it is for
A health care provider may use protein C and protein S tests to: To determine whether you have a protein C or S deficiency , your provider will measure these proteins' activity. These are called protein C and protein S functional tests, and they can show whether one or both of these proteins are the cause of any clotting problems. Source: MedlinePlus, National Library of Medicine. Medical test information is public domain. Source identity and definition checked automatically on 2026-10-18. No individual clinical interpretation or human reviewer is asserted.
Limitations
Reference intervals and interpretation depend on the laboratory, specimen, method and clinical context. This source definition is educational information; it does not establish a diagnosis, product approval or suitability for an individual.
Also known as
- protein C antigen, protein S antigen, PC, PS, free PS, autoprothrombin IIA
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