Description
Why It’s Done
This test is typically ordered to:
• Evaluate unexplained blood clots (deep vein thrombosis, pulmonary embolism).
• Diagnose a Protein S deficiency, which may be inherited or acquired.
• Monitor clotting risk in people with family history of thrombosis.
• Investigate recurrent miscarriages or clotting problems during pregnancy.
• Assess clotting risk before major surgeries or in cases of long-term immobility.
A deficiency in Protein S can increase the risk of developing dangerous blood clots.
Preparation
• Fasting: Not usually required, but follow your doctor’s instructions.
• Medications: Certain medications (e.g., warfarin, oral contraceptives) can affect Protein S levels. Your doctor may advise stopping them temporarily before the test.
• Timing: Avoid testing during acute illness, pregnancy, or shortly after a blood clot, as results may be temporarily abnormal.
• Sample Type: A blood sample is drawn from a vein in your arm.
