Background: Methemoglobinemia is a rare condition in which there is an elevated level of methemoglobin in the blood resulting in its reduced oxygen carrying capacity, which can be induced by substances used routinely by dentists. Case Report: The author details the unanticipated event of methemoglobinemia in a 41 year old male with hypodontia undergoing anaesthetia for dental implants. An abnormal appearance of the blood followed by dropping oxygen saturation intra-operatively aided this potentially fatal diagnosis. Acute management included the delivery of methylene blue followed by liaison with hematologists to plan future procedures. Conclusion: Methemoglobinemia is of direct relevance to the dental setting in patients being administered anaesthesia.