Protein S

What the risks are:

• excessive bleeding
• fainting or feeling lightheaded
• hematoma (blood accumulating under the skin)
• infection (a slight risk any time the skin is broken)
• multiple punctures to locate veins

Special considerations:

Protein C and Protein S are decreased by Vitamin K antagonist oral anticoagulants (Coumadin, warfarin). Measurements of Protein C or S may be difficult to interpret in patients taking oral anticoagulants During an acute thrombotic episode, Proteins C and S are reduced even if decreased C or S is not the cause of the thrombosis, and measurements of Protein C or S may be misleading until the acute episode is resolved.

Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.