Empiric therapy or empirical therapy is medical treatment or therapy based on experience[1] and, more specifically, therapy begun on the basis of a clinical "educated guess" in the absence of complete or perfect information. Thus it is applied before the confirmation of a definitive medical diagnosis or without complete understanding of an etiology, whether the biological mechanism of pathogenesis or the therapeutic mechanism of action. The name shares the same stem with empirical evidence, involving an idea of practical experience.
Empiric antimicrobial therapy is directed against an anticipated and likely cause of infectious disease. It is used when antimicrobials are given to a person before the specific bacterium or fungus causing an infection is known. When it becomes known, treatment that is used is called directed therapy. Fighting an infection sooner is important to minimize morbidity, risk, and complications for serious infections like sepsis and suspected bacterial meningitis.