Answer
5. The abuse of erthropoietin (doping) results in the production of too many red blood cells (RBCs), a form of polycythemia.
Work Step by Step
The abnormally large number of RBCs increases the viscosity of the blood, and clogs the small blood vessels; consequently, the heart has to work harder to pump the blood around the body.
Adverse effects of polycythemia include dyspnea, headaches, tinnitus, dizziness, spleen damage, stroke and heart attack/myocardial infarction.