Hepatic peptide hormone hepcidin is the key regulator of iron metabolism and the mediator of anemia of inflammation. Previous studies indicated that interleukin-6 (IL-6) mediates hepcidin increase and consequent hypoferremia during inflammation. Here we used an in vivo human endotoxemia model to analyze the effects of lipopolysaccharide (LPS) as a more upstream inflammation activator. The temporal associations between plasma cytokines, hepcidin levels, and serum iron parameters were studied in 10 healthy individuals after LPS injection. IL-6 was dramatically induced within 3 hours after injection, and urinary hepcidin peaked within 6 hours, followed by a significant decrease in serum iron. Serum prohepcidin showed no significant change within a 22-hour time frame. These in vivo human results confirm the importance of the IL-6-hepcidin axis in the development of hypoferremia in inflammation and highlight the rapid responsiveness of this iron regulatory system.