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Protein C and Protein S

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Also known as: Protein C Activity; Protein C Level; Protein S Activity; Protein S Level
Formal name: Protein C, Functional or Antigen; Protein S, Functional or Antigen (Free or Total)

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At a Glance

Why Get Tested?

To help evaluate inappropriate blood clot formation (thrombotic episode or thromboembolism); to determine whether you may have a protein C or protein S deficiency

When to Get Tested?

When you have had an unexplained blood clot; when your newborn has a severe clotting disorder; sometimes when a close relative has an inherited protein C or protein S deficiency

Sample Required?

A blood sample drawn from a vein in your arm

Test Preparation Needed?

You must wait at least 10 days after a thrombotic episode and be off oral warfarin (Coumadin®) anticoagulant therapy for 2 weeks before having this test done. (See also Common Questions #1.)