Aspirin is a blood thinner. Aspirin is an anti-platelet medication that thins the blood by preventing blood cells from clotting, according to MedlinePlus. Doctors may recommend aspirin or other blood-thinning medications to individuals with heart disease or hindered blood flow to the brain.
While aspirin is beneficial in minimizing the risk of blood flow conditions, such as stroke and heart attack, the medication is associated with certain side effects, according to the Food and Drug Administration. Serious side effects of aspirin include kidney failure, brain bleeding and stomach bleeding. Taking aspirin in conjunction with alcohol or additional medications that contain aspirin may increase the risk of severe side effects.