Unfractionated heparin (UFH) and low molecular weight heparin (LMWH) are commonly used to prevent VTE in ICU and non-ICU patients. HIT, an untoward consequence of exposure to heparin is an immune disorder that may develop in patients treated with heparin products. HIT is antibody mediated, usually due to IgG antibodies directed against epitopes on the platelet surface comprised of the heparin-platelet factor 4 complex. HIT is generally characterized by a decrease in platelet count to less than 100 X 109/L, or a 50% decrease from baseline, after exposure to heparin. HIT is typically observed after 5 to 10 days of treatment. Alternatively, patients with previous exposure to heparin can develop HIT in two days while heparin naive patients may develop HIT in about 10 days. The platelet count usually returns to normal several days after discontinuing heparin with or without therapy, though the risk for thrombosis persists for up to 3 months due to the persistence of antibodies.