Sepsis is a serious medical condition caused by a severe infection. The more critical subsets of sepsis include severe sepsis (sepsis with acute organ dysfunction) and septic shock (sepsis with refractory arterial hypotension). If a proven source of infection is lacking but the other criteria of sepsis are met, the condition typically meets the criteria for systemic inflammatory response syndrome (SIRS); the exception is the condition greater than 10% band forms (this is not a part of the SIRS definition).
Septicemia is sepsis of the bloodstream caused by bacteremia, which is the presence of bacteria in the bloodstream. The term septicemia is also used to refer to sepsis in general.