Methaemoglobinaemia

Author: Frances Balmer / Editor: Jason Kendall / Reviewer: Rebecca Ford, Frances Balmer / Codes: A1, A4, PP2, R2 / Published: 16/05/2022 / Reviewed: 08/01/2026

Methaemoglobinaemia is a life-threatening cause of hypoxia and death but is reversible with early recognition and treatment.

This module provides an understanding of the underlying pathophysiology and causative agents, discusses how to identify and assess the patient with methaemoglobinaemia, and provides an evidence-based guide to treatment in line with the National Poisons Information Service and best practice.

Learning Objectives:

  • Understand the pathophysiology and clinical manifestation of methaemoglobinaemia
  • Recognise the need to screen for underlying causes of methaemoglobinaemia and modifying treatment according to cause
  • Appreciate the effect of methaemoglobin on oximetry and the limitations of SpO2 monitoring
  • Be able to perform risk stratification to identifying those patients who need active treatment
  • Gain a detailed knowledge of the pharmacological profile and risk/benefits of methylene blue use to facilitate safe prescribing.

START MODULE

References

  1. Wright RO, Lewander WJ, Woolf AD. Methemoglobinemia: etiology, pharmacology, and clinical management. Ann Emerg Med. 1999 Nov;34(5):646-56.
  2. Iolascon A, Bianchi P, Andolfo I, et al. Recommendations for diagnosis and treatment of methemoglobinemia. Am J Hematol. 2021 Sep 23;96(12):16661678
  3. Hanukoglu A, Danon PN. Endogenous methemoglobinemia associated with diarrheal disease in infancy. J Pediatr Gastroenterol Nutr. 1996 Jul;23(1):1-7.
  4. Ralston AC, Webb RK, Runciman WB. Potential errors in pulse oximetry. III: Effects of interferences, dyes, dyshaemoglobins and other pigments. Anaesthesia. 1991 Apr;46(4):291-5.
  5. National Poisons Information Service (NPIS). Methylthioninium chloride antidote. Available here. [Cited on 11/04/2025].
  6. El-Husseini A, Azarov N. Is threshold for treatment of methemoglobinemia the same for all? A case report and literature review. Am J Emerg Med. 2010 Jul;28(6):748.e5-748.e10.
  7. Rino PB, Scolnik D, et al., Ascorbic acid for the treatment of methemoglobinemia: the experience of a large tertiary care pediatric hospital. Am J Ther. 2014 Jul-Aug;21(4):240-3.
  8. Wright RO, Magnani B, Shannon MW, Woolf AD. N-acetylcysteine reduces methemoglobin in vitro. Ann Emerg Med. 1996 Nov;28(5):499-503.
  9. Ferris D. BestBet : Methylene blue as a treatment for methaemoglobinaemia. 2010 Available here. 
  10. Youngster I, Arcavi L, Schechmaster R, Akayzen Y, Popliski H, Shimonov J, Beig S, Berkovitch M. Medications and glucose-6-phosphate dehydrogenase deficiency: an evidence-based review. Drug Saf. 2010 Sep 1;33(9):713-26.
  11. National Poisons Information Service (NPIS). Toxbase. Methaemoglobinaemia. [Cited on 11/04/2025].

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