Beware of bleeding. In addition to lowering the blood's ability to clot, aspirin also inhibits helpful substances that protect the stomach's delicate lining, creating a double whammy effect. As a result, stomach upset or bleeding in the stomach and intestines can occur. If you take daily low-dose aspirin and your stomach starts bothering you, call your doctor, says Dr. Cannon. With minor bleeding, a blood test may reveal a low red blood cell count (anemia).