During the course of evolution, our immune system has eventually developed to deal with infectious pathogen invasions by various host defense mechanisms. Inflammatory response is one of the primary responses to a microbial invasion, which leads to the systemic illness which is referred to as sepsis. Its severity correlates with mortality. It may occur as a result of infections acquired from community, hospitals or other healthcare facilities. There is an alarming number of 18 million new sepsis cases reported each year worldwide with mortality rate ranging from 30–50% Early diagnosis and prompt antimicrobial therapy is crucial in the treatment of sepsis for saving lives. Sepsis is a systemic inflammatory response syndrome (SIRS) that affect all organs. Hence, host responses including cytokine, cell markers, receptor biomarkers, coagulations, vascular endothelial damage, vasodilation, organ failure and scientific advancement in the field of molecular biology can equip us to screen wide range of protein markers in acute phase of sepsis development that helps in identifying relevant biomarkers to diagnose sepsis. The actual mechanism of production of PCT during infection is not known, but it assumes that bacterial lipopolysaccharides and sepsis released cytokines modulate the liver and peripheral blood mononuclear cells to produce PCT. Microbial infection induces the elevated expression of CALC 1 gene followed by the release of PCT product which is correlated with severity of disease and mortality.