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Carbon monoxide poisoning - Symptoms of carbon monoxide poisoning

NHS Choices Medical Reference

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A headache is the most common symptom of carbon monoxide poisoning.

Other common symptoms include:

  • dizziness and nausea (feeling sick)
  • vomiting (being sick)
  • tiredness and confusion
  • stomach pain
  • shortness of breath and difficulty breathing

Symptoms of carbon monoxide

poisoning can be similar to those of food poisoning and flu. However, unlike flu, carbon monoxide poisoning does not cause a high temperature (fever).

Your symptoms may be less severe when you are away from the source of the carbon monoxide.

The longer you inhale CO gas, the worse your symptoms will be. You may lose balance, vision and memory. Eventually, you may lose consciousness. This can happen within two hours if there is a lot of CO gas in the air.

However, symptoms of carbon monoxide poisoning can sometimes occur days or months after breathing in carbon monoxide.

Symptoms of CO poisoning that develop later include:

  • confusion
  • memory loss
  • co-ordination problems

High levels of carbon monoxide

If you have breathed in high levels of CO gas, it is likely that you will experience more severe symptoms. These may include:

  • impaired mental state and personality changes (intoxication)
  • vertigo - the feeling that you or the environment around you is spinning
  • ataxia - loss of physical co-ordination due to underlying damage to the nervous system and brain
  • breathlessness and tachycardia (a heart rate of more than 100 beats a minute)
  • chest pain caused by angina or a heart attack
  • seizures - an uncontrollable burst of electrical activity in the brain that causes muscle spasms
  • loss of consciousness - in cases where there are very high levels of CO gas, death may occur within minutes

At risk groups

Certain people in your household may be affected by carbon monoxide poisoning more quickly than others. Those at particular risk include:

  • babies and young children
  • pregnant women
  • people with heart or breathing problems

Pets may be the first to show signs of carbon monoxide poisoning because they are vulnerable to the effects of CO gas. The smaller an animal or a person is, the faster CO gas will affect them.

If your pet suddenly becomes ill or dies unexpectedly, and death is not related to old age or an existing health condition, you should investigate the possibility of a CO leak.

Medical Review: April 15, 2012
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