Hemodialysis machines are equipped with a blood leak detector/alarm to prevent loss of blood following rupture of semipermeable membrane; the blood leak alarms could also be triggered by sensor malfunction or presence of air bubbles in the system. Hydroxocobalamin is a Food and Drug Administration-approved rapid-acting antidote to cyanide poisoning that converts cyanide to nontoxic cyanocobalamin. Side effects are reddish discoloration of skin and body fluids, urticarial rash, and rarely anaphylaxis. In this article, a case of false blood leak alarm following treatment of cyanide poisoning with hydroxocobalamin is reported, wherein the blood leak detector in dialysis machines prevented the patient from undergoing hemodialysis by repeatedly activating blood leak alarms. Continuous renal replacement therapy was used to overcome this problem. As the use of hydroxocobalamin increases, health care professionals should be educated about its potential to interfere with hemodialysis.