Platelets are small, round blood cells that help with blood clotting. Also known as thrombocytes, platelets play an important role in healthy blood functions and platelet function tests are widely used to evaluate how well a person’s platelets work to stop bleeding within the body. A normal platelet count is from 150,000 to 450,000 per microliter of blood, and can be both too high or too low, known as thrombocytopenia. A normal platelet count can still be problematic if the cells are functioning poorly, known as platelet dysfunction.

Platelets are produced in the bone marrow and circulated within the bloodstream, where they will arrive to injury sites and start the clotting process. Platelets achieve clotting in three ways:

• Adhere to the injury site by growing tentacles that attach to each other and the injured surface
• Aggregate to form a plug on the injury site
• Release compounds that stimulate further aggregation and guide immune cells to the injury site