Hemolysis is the term for accelerated destruction of red blood cells (RBCs), meaning a shortened RBC lifespan. Depending upon the rate and duration of hemolysis and the erythropoietic response, anemia may or may not occur. If the degree of hemolysis is modest and the erythropoietic response of the bone marrow completely compensates for the decreased RBC lifespan, then the hemoglobin concentration may remain normal, producing a state called compensated or fully compensated hemolysis. If the erythropoietic response is insufficient to completely compensate for hemolysis, then anemia occurs, producing a state called uncompensated or incompletely compensated hemolysis. In common usage, the descriptor “hemolytic anemias” refers to both uncompensated and compensated hemolytic states, even though anemia may not always be present.