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Asked by: Ivy Mallory
School:Owego Elementary School
Teacher:Mrs. Elliker
Career Interest:N/A


Answered by: Kelly Storrs
Title:Clinical Instructor, Binghamton University
Department:Decker School of Nursing
About Scientist:N/A


Date: 05-18-2006

Question: What makes aspirin thin your blood?

Answer: Contrary to belief, aspirin does not actually thin the blood. Aspirin is a platelet aggregation inhibitor, which simply means that is prevents blood from forming clots. Platelets are particles in the blood that are necessary to form blood clots. When platelets are bound together with fibrin (a protein found in blood), a blood clot is formed.

Blood clots are important because they stop the bleeding when we get cut. However, if a blood clot forms in an artery, it blocks the flow of blood to the tissue in that area of the body and tissue becomes damaged. For example, when a blood clot forms in an artery supplying blood to the heart, it causes a heart attack, and when a blood clot forms in the brain, it causes a stroke.

Aspirin works to block the formation of blood clots by preventing platelets from forming clumps. It does this by blocking a chemical that the platelets produce which causes them to clump. When aspirin is taken, it prevents the platelets from forming clumps for days after taking it. So if we were to get a cut after taking aspirin, it is difficult to stop the bleeding without the platelets binding to the fibrin and forming a blood clot. This is why aspirin appears to make the blood thinner.

Ask a Scientist appears Thursdays. Questions are answered by faculty at Binghamton University.  Teachers in the greater Binghamton area who wish to participate in the program are asked to write to Ask A Scientist, c/o Binghamton University, Office of Communications and Marketing, PO Box 6000, Binghamton, NY 13902-6000 or e-mail Check out the Ask a Scientist Web site at To submit a question, download the submission form(.pdf, 460kb).

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Last Updated: 6/22/10