The operating theatre where human blood looked green

When doctors preparing a patient for surgery drew arterial blood, its dark green appearance demanded an explanation. The case appeared in The Lancet in June 2007, although the hospital admission had occurred in October 2005. The patient was a 42-year-old man with compartment syndrome affecting both lower legs. His regular medicines included the migraine treatment sumatriptan, reportedly taken at 200 mg daily for several months. [1]

The diagnosis was sulfhaemoglobinaemia: an unusual alteration of haemoglobin, the protein that normally carries oxygen in red blood cells. Sulphur becomes incorporated into the haem structure, producing a pigment that can give blood a greenish appearance and impair oxygen transport. A related report by the clinicians described the case as associated with sumatriptan. Association in a case report should not be mistaken for proof that every person taking that medicine faces the same outcome. [2]

This was a documented medical observation, not evidence of an alien patient or paranormal transformation. Its strangeness lies in chemistry: changing an oxygen-carrying molecule can change both its performance and the colour that clinicians expect to see. [1][2]

Editorial note: This feature summarises the published sources listed below; it is not a new archive investigation. The accompanying image is AI-generated illustration, not an archival photograph or evidence of the event.