Severe anaemia, with haemoglobin (Hb) levels ≤3 g dL−1, is associated with mortality rates of 50–95%. Although accepted transfusion targets have been debated in the literature (Carson et al., 2002; Practice guidelines for blood component therapy. 1996; Consensus Conference. 1988; Hebert et al., 1999), few would argue the risks associated with Hb levels less than 5 g dL−1 in critically ill patients. In patients who are unable to receive red blood cell transfusions, the utility of Hb solutions is an attractive solution. We describe a Jehovah's Witness patient who exemplifies the marked physiologic derangements of severe anaemia and subsequent clinical resolution with large volume polymerized human Hb transfusion. The Hb-based oxygen carrier, PolyHeme®, provided adequate oxygen transport, acting as a bridge until endogenous production could compensate for red cell loss. Practicing physicians need to be aware of current therapeutic options for use in these complicated patients.