Poisoning - Symptoms 

Symptoms of poisoning 

The symptoms of poisoning depend on the substance and the amount you take in.

Some poisonous substances, such as carbon monoxide, interfere with the blood's ability to carry oxygen. Others, such as bleach, burn and irritate the digestive system.

Parents and carers should be aware of sudden, unexplained illness in young children, particularly if they are drowsy or unconscious, as poisoning could be the cause.

If you suspect that someone has swallowed a poisonous substance, seek immediate medical advice. Read more about what to do if you think someone has been poisoned.

General symptoms

General symptoms of poisoning can include:

  • feeling sick
  • being sick
  • diarrhoea
  • stomach pain
  • drowsiness, dizziness or weakness
  • high temperature of 38°C (100.4°F) or above
  • chills (shivering)
  • loss of appetite
  • headache
  • irritability
  • difficulty swallowing (dysphagia)
  • breathing difficulties
  • producing more saliva than normal
  • skin rash
  • blue lips and skin (cyanosis)
  • burns around the nose or mouth
  • double or blurred vision
  • mental confusion
  • seizures (fits)
  • loss of consciousness
  • coma (in severe cases)

Signs of a medication or drug overdose

Medication overdoses are the most common type of poisoning in the UK. If you take too much of a medicine, you may experience symptoms specific to the medication taken, as well as the more general symptoms listed above.

Some of the most common medications or drugs involved in cases of poisoning are listed below.


Paracetamol is a widely used over-the-counter painkiller.

Specific signs of paracetamol poisoning include:

  • yellowing of the skin and the whites of the eyes (jaundice)
  • loss of co-ordination
  • low blood sugar (hypoglycaemia), which can cause symptoms including sweating, trembling and irritability


Aspirin was used as a painkiller in the past but is now increasingly used for its blood-thinning properties to prevent blood clots.

Specific signs of aspirin poisoning include:

Tricyclic antidepressants

Tricyclic antidepressants are used to treat depression as well as a number of other mental health conditions such as panic disorder and obsessive compulsive disorder (OCD). Some types of tricyclic antidepressants can also be used to treat nerve pain.

Specific signs of poisoning with tricyclic antidepressants include:

  • excitability
  • dry mouth
  • large pupils
  • irregular or rapid heartbeat
  • low blood pressure, which can cause symptoms including lightheadedness and fainting

Selective serotonin reuptake inhibitors (SSRIs)

SSRIs are a newer type of antidepressant that are also used to treat a number of other mental health conditions such as OCD and anxiety disorder.

Specific signs of SSRI poisoning include:

  • feeling agitated
  • tremor (shaking)
  • uncontrolled movement of the eyes (nystagmus)
  • severe muscle tension


Beta-blockers are used to treat a number of conditions that affect the heart or blood such as high blood pressure, angina and heart failure.

Specific signs of poisoning with beta-blockers include:

  • low blood pressure, which can cause symptoms including lightheadedness and fainting
  • a slow heartbeat (below 60 beats a minute)

Calcium-channel blockers

Calcium-channel blockers are used in the treatment of high blood pressure and angina.

Specific signs of calcium-channel blocker poisoning include:

  • feeling agitated
  • low blood pressure, which can cause symptoms including lightheadedness and fainting
  • chest pain
  • a slow heartbeat (below 60 beats a minute)


Benzodiazepines are a type of tranquiliser often used on a short-term basis to treat anxiety and sleeping problems (insomnia).

Specific signs of poisoning with benzodiazepines include:

  • co-ordination and speech difficulties
  • uncontrolled movement of the eyes (nystagmus)
  • shallow breathing


Opioids are a type of stronger painkillers used to treat moderate to severe pain. Opioids include codeine and morphine as well as the illegal drug heroin.

Specific signs of opioid poisoning include:

  • small pupils
  • shallow breathing

Stimulant overdose

If you take too much of a stimulant-like drug such as cocaine, amphetamine, crack or ecstasy, overdose signs can include:

  • anxiety and paranoia (feeling that people are out to get you)
  • feeling restless or agitated
  • hallucinations (seeing or hearing things that are not real)
  • high temperature
  • chest pain
  • rapid breathing
  • irregular or fast heartbeat

Cannabis overdose

If you smoke (or eat) too much cannabis then you may experience the following symptoms:

  • paranoia
  • hallucinations
  • numbness in your arms and legs

Page last reviewed: 23/08/2013

Next review due: 23/08/2015


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