Symptoms of Carbon Monoxide Poisoning

How can you know if you have carbon monoxide poisoning?

Carbon monoxide poisoning is a chameleon in the medical world. Its symptoms mimic many other conditions and there is not a single symptom that is the gold standard of all carbon monoxide poisonings. In other words, it's very difficult to identify, but there are a few changes you should be aware of.

An illustration with common symptoms of carbon monoxide poisoning

Illustration by Jessica Olah for Verywell Health

Frequent Symptoms

The most common symptoms of carbon monoxide poisoning are vague and related to many conditions.

Early Symptoms

Carbon monoxide binds to the hemoglobin to create a molecule called carboxyhemoglobin (COHb), which interferes with the body's ability to transport and use oxygen, especially in the brain. Because of that, the symptoms are similar to those of other conditions that affect the brain and cause a decrease in oxygenation (known as hypoxia):

  • Headache
  • Nausea
  • Dizziness
  • Fatigue

Because it is a gas and will usually affect everyone exposed to it, carbon monoxide is easier to identify when the symptoms strike several people at once. Due to its chameleon-like nature, it's still not an easy task. Headaches and nausea in isolation rarely cause anyone to think of carbon monoxide poisoning as the most likely culprit.

Even so, when carbon monoxide affects multiple patients at the same time, it is often dismissed as an infection or bad food rather than carbon monoxide exposure.

Progressed Symptoms

As carbon monoxide poisoning progresses, symptoms get more serious, but are still extremely vague and difficult to identify as specific to carbon monoxide exposure:

  • Confusion
  • Shortness of breath
  • Chest pain
  • Vomiting
  • Blurry or double vision
  • Loss of consciousness

There is not a clear timeline to show how long it takes to progress from a headache to loss of consciousness.

Carbon monoxide exposure is time- and concentration-dependent, meaning the amount of carbon monoxide in the air is as important as how long the patient remains exposed to it.

Rare Symptoms

A deep red, flushed skin color (cherry red) is the one telltale indicator of carbon monoxide poisoning. It comes from high levels of carboxyhemoglobin in the blood.

Unfortunately, it is often a postmortem examination that reveals such a bright red coloring. The level of carbon monoxide in the blood required to get the skin to that color is so high that it is nearly always fatal.

So extremely flushed skin is too late a sign to be useful in determining if a patient is suffering from carbon monoxide poisoning.

To be treated successfully, carbon monoxide poisoning must be recognized long before the patient turns bright red.

Long-Term Complications

As common as carbon monoxide poisoning is, there is a lot we still do not understand about this condition. Long-term exposure to elevated levels of carbon monoxide—even when the levels aren't that high, but the exposure continues for many days or weeks—can lead to peripheral artery disease, cardiomyopathy, and long-term, poorly understood neurological problems.

Damage to the brain is a significant injury incurred by many patients with carbon monoxide poisoning. Patients can develop neurological complications (difficulty concentrating, memory loss, tremors, trouble speaking, etc.) at the same time as the carbon monoxide poisoning or at a later time. When the neurological signs and symptoms show up later, it's known as delayed neurologic sequelae (DNS).

Research continues into why this happens and how to identify the potential for long-term symptoms. For example, pupil constriction in the eye might predict how the brain will react more than 30 days after exposure. One study that followed patients for years after they were exposed discovered that these patients were more likely than those without a history of carbon monoxide poisoning to develop peripheral artery disease.

There is very little evidence-based treatment for carbon monoxide poisoning. Most options focus on removing the carbon monoxide as quickly as possible. These treatments range from basic high-flow oxygen delivery (15-25 liters per minute) provided at normal atmospheric pressures all the way to lights being placed into the lungs to separate carbon monoxide from the hemoglobin, or hyperbaric oxygen therapy that is delivered at higher than normal atmospheric pressures.

When to See a Healthcare Provider

Carbon monoxide poisoning is very serious and always warrants a trip to see the healthcare provider. The carbon monoxide gets stuck in the bloodstream, and it takes up to several hours to remove it.

Anytime carbon monoxide poisoning is suspected, call 911. Don't wait for help. Move to fresh air immediately. Usually, it's best to go outside while waiting for the ambulance.

When you see the healthcare provider, note that history is more important than symptoms. The most important way to recognize carbon monoxide poisoning is by recognizing the danger signs of behaviors leading up to the moment that symptoms started appearing.

Faulty stoves, fireplaces, or wood-burning appliances are usually to blame for carbon monoxide poisoning in the home. Cars and trucks are common culprits in the business setting, as well as various other sources of carbon monoxide poisoning.

Your healthcare provider may ask you to describe how long the symptoms took to become bad enough to seek help. What was going on during that time? Is it cool weather and some of the family had decided to start the barbecue under the patio? This information can help confirm that your symptoms are truly caused by carbon monoxide poisoning.

Frequently Asked Questions

  • How does carbon monoxide affect the body?

    Carbon monoxide (CO) affects the body by impairing the ability of red blood cells to carry oxygen. This ends up starving the internal organs of oxygen. The heart and brain in particular require large amounts of oxygen to function properly. The damage CO does to the body is cumulative, which is why prompt treatment is vital.

  • How long does it take to get carbon monoxide poisoning?

    How long it takes to get carbon monoxide poisoning depends on how much gas is in the air and length of exposure. If CO levels are high, within a couple of hours, you may experience problems with balance, vision, and memory, and even lose consciousness.

  • Do low levels of carbon monoxide poisoning look similar to other conditions?

    Yes, low levels of carbon monoxide poisoning can look similar to other conditions like the flu. Low levels of CO breathed in over an extended period of time can cause flu-like symptoms such as headache, nausea, and fatigue. One clue these symptoms may be associated with carbon monoxide is a lack of fever.

2 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. University of Iowa Hospitals & Clinics. Carbon Monoxide: Knowing the Answer to These Six Questions Could Save Your Life.

  2. National Health Service (NHS). Carbon Monoxide Poisoning.

Additional Reading

By Rod Brouhard, EMT-P
Rod Brouhard is an emergency medical technician paramedic (EMT-P), journalist, educator, and advocate for emergency medical service providers and patients.