Carbon monoxide poisoning

Overview 
Theory 
Diagnosis 
Management 
Follow up 
Resources 

Last reviewed: 18 Jun 2025

Last updated: 19 Dec 2024

Carbon monoxide (CO) poisoning results in significant morbidity and mortality.

Poisoning can occur following exposure to a variety of fire or nonfire sources, including gas and charcoal grills, motor vehicle exhaust and other engine exhausts in poorly ventilated spaces, and various industrial sources. It can also occur due to endogenous production by the liver after inhalational exposure to methylene chloride, a component of some paint strippers.

Early symptoms are nonspecific and include headache, dizziness, and nausea.

If symptoms of CO poisoning are suspected, individuals should leave the building or space immediately and call the emergency medical services.

Diagnosis is based on a clinical triad: history of CO exposure, elevated carboxyhemoglobin levels, and symptoms/signs consistent with CO poisoning.

Severe poisoning may result in cardiovascular manifestations (e.g., myocardial ischemia, myocardial infarction, cardiac dysfunction, dysrhythmias, cardiac arrest). Neurologic symptoms include acute stroke-like symptoms, altered mental status, confusion, coma, and syncope.

High-flow oxygen therapy and supportive therapy are key treatments. Hyperbaric oxygen therapy should be considered in select patients.

Around 40% to 50% of survivors of CO poisoning suffer from delayed neurocognitive deficits that can become permanent.

Definition

Carbon monoxide (CO) is a poisonous gas produced through burning fuel. When inhaled in large quantities, CO enters the bloodstream and binds to hemoglobin molecules with a much greater affinity than oxygen, creating carboxyhemoglobin.[1] The binding of CO results in tissue hypoxia and impairment of cellular respiration, and direct effects of CO toxicity at the cellular level. CO poisoning can present in patients as a wide range of acute and chronic symptoms.[1][2]

History and exam

Key diagnostic factors

exposure to incomplete combustion of carbon-containing material
exposure to fire with smoke inhalation
nausea
headache
vomiting
blurred vision
dizziness
vertigo
altered consciousness
dyspnea
tachycardia
hypotension or hypertension
cardiac arrhythmias
pain
weakness
sleep changes
irritability
flu-like symptoms

Full details

Other diagnostic factors

exposure to methylene chloride
delayed neuropsychiatric features
other severe neurologic symptoms
cutaneous blistering
pulmonary edema
cardiac arrest
focal neurologic abnormalities (e.g., hemiplegia, truncal ataxia)
disseminated intravascular coagulation

Full details

Risk factors

exposure to incomplete combustion of carbon-containing material
exposure to fire with smoke inhalation
exposure to methylene chloride

Full details

Diagnostic tests

1st tests to order

carboxyhemoglobin level
ECG
cardiac monitoring
blood glucose
complete blood count
urea and electrolytes
creatinine
lactate
pH level
cardiac biomarkers
creatine kinase

Full details

Tests to consider

chest x-ray
Mini Mental State Examination
CT head
magnetic resonance imaging and spectroscopy
liver function tests
pregnancy test

Full details

Treatment algorithm

ACUTE

all patients

Contributors

Expert advisers

Richard Moon, MD

Professor of Anesthesiology

Professor of Medicine

Division of Pulmonary, Allergy and Critical Care Medicine

Duke University

Durham

Disclosures

RM has been reimbursed by Merck for contributions to the Merck Manual.

Acknowledgements

Dr. Richard Moon would like to gratefully acknowledge Dr Jason Rose and Dr Prasanthi Govindarajan, previous contributors to this topic.

Disclosures

PG declares that she has no competing interests. JR is a co-inventor on patent applications for the use of heme-based molecules as antidotes for CO poisoning. JR is a shareholder, officer, and director of Globin Solutions, Inc. Globin Solutions, Inc. has an exclusive license to this technology. Globin Solutions, Inc. had an option agreement to technology directed at using hydroxycobalamin for CO poisoning from Virginia Commonwealth University in the last 12 months. JR is an author of publications cited within this topic.

Peer reviewers

Richard S. Weisman, PharmD

Director

Florida Poison Center

Miami

Disclosures

RSW declares that he has no competing interests.

Sean Patrick Nordt, MD, PharmD

Resident Physician

Department of Emergency Medicine

University of California

San Diego

Disclosures

SPN declares that he has no competing interests.

Paul Hamilton, MD

Director

Department of Emergency Medicine

Mount Sinai School of Medicine

New York

Disclosures

PH declares that he has no competing interests.

Ruben Thanacoody, MD, FRCP(Edin)

Consultant Physician and Clinical Toxicologist

Regional Drugs and Therapeutics Centre

Newcastle-upon-Tyne

Disclosures

RT declares that he has no competing interests.

References

Our in-house evidence and editorial teams collaborate with international expert contributors and peer reviewers to ensure that we provide access to the most clinically relevant information possible.

Key articles

Hampson NB, Piantadosi CA, Thom SR, et al. Practice recommendations in the diagnosis, management, and prevention of carbon monoxide poisoning. Am J Respir Crit Care Med. 2012 Dec 1;186(11):1095-101.Full text Abstract

Centers for Disease Control and Prevention. Clinical guidance for carbon monoxide poisoning following disasters and severe weather. Jul 2024 [internet publication].Full text

Wolf SJ, Maloney GE, Shih RD, et al; American College of Emergency Physicians Clinical Policies Subcommittee (Writing Committee) on Carbon Monoxide Poisoning. Clinical policy: critical issues in the evaluation and management of adult patients presenting to the emergency department with acute carbon monoxide poisoning. Ann Emerg Med. 2017 Jan;69(1):98-107.e6.Full text Abstract

Weaver LK. Carbon monoxide poisoning. Undersea Hyperb Med. 2020 First Quarter;47(1):151-69.Full text Abstract

Reference articles

A full list of sources referenced in this topic is available to users with access to all of BMJ Best Practice.

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- Clinical policy: critical issues in the evaluation and management of adult patients presenting to the emergency department with acute carbon monoxide poisoning
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Carbon monoxide poisoning

Summary

Definition

History and exam

Key diagnostic factors

Other diagnostic factors

Risk factors

Diagnostic tests

1st tests to order

Tests to consider

Treatment algorithm

all patients

Contributors

Expert advisers

Richard Moon, MD

Disclosures

Acknowledgements

Disclosures

Peer reviewers

Richard S. Weisman, PharmD

Disclosures

Sean Patrick Nordt, MD, PharmD

Disclosures

Paul Hamilton, MD

Disclosures

Ruben Thanacoody, MD, FRCP(Edin)

Disclosures

References

Key articles

Reference articles

A full list of sources referenced in this topic is available to users with access to all of BMJ Best Practice.

Differentials

Guidelines

Patient information

Log in or subscribe to access all of BMJ Best Practice

Log in or subscribe to access all of BMJ Best Practice

Log in to access all of BMJ Best Practice