Which symptoms are associated with higher levels of methemoglobin?

Updated: Dec 09, 2018
  • Author: Mary Denshaw-Burke, MD, FACP; Chief Editor: Emmanuel C Besa, MD  more...
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Symptoms are proportional to the fraction of methemoglobin. A normal methemoglobin fraction is about 1% (range, 0-3%). Symptoms associated with higher levels of methemoglobin are as follows:

  • 3-15% - Slight discoloration (eg, pale, gray, blue) of the skin
  • 15-20% - Cyanosis, though patients may be relatively asymptomatic
  • 25-50% - Headache, dyspnea, lightheadedness (even syncope), weakness, confusion, palpitations, chest pain
  • 50-70% - Abnormal cardiac rhythms; altered mental status, delirium, seizures, coma; profound acidosis
  • >70% - Usually, death

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