Subcutaneous heparin is commonly used as a prophylaxis against deep venous
thrombosis in a wide variety of hospitalized patients. As with most medicat
ions, heparin has a significant side effect profile; heparin-induced hyperk
alemia is an unusual but well described side effect. To increase awareness
of heparin-induced hyperkalemia and of those patients; at greatest risk, we
present two cases of documented hyperkalemia induced by I heparin and reco
nfirmed by drug rechallenge.