At a glance

Also known as


Why get tested?

In order to establish a diagnosis of paracetamol over dosage, to assess risk of liver damage and to decide on the need for protective, antidotal therapy

When to get tested?

Four hours after a single overdose, or as soon as possible after that, and immediately if more than one overdose has been taken within the last 1 or 2 days. It is best to treat an overdose within 8 hours whenever possible.

Testing may be ordered when a person has signs and symptoms of an overdose. These can appear as early as 2 to 3 hours after ingestion or may not occur for 12 or more hours. Some of these include:

  • Nausea, vomiting, diarrhea
  • Loss of appetite
  • Abdominal pain or cramping
  • Irritability
  • Sweating

If untreated, toxicity can progress within 3 to 4 days to include jaundice, liver and kidney failure, convulsions, coma and death. If treatment is received within 8 hours of the overdose, however, there is a very good chance of recovery.

Sample required?

A blood sample drawn from a vein usually in an arm

What is being tested?

The plasma paracetamol concentration is being measured

How is the sample collected for testing?

Normally from a vein in the arm by use of a needle and syringe

The Test

How is it used?

The plasma paracetamol concentration is used to establish a diagnosis of paracetamol over dosage and to help decide on the need for treatment.

When is it requested?

Only when paracetamol over dosage is a possibility.

What does the test result mean?

The plasma paracetamol concentration at a known time point between 4 and 15 hours after a single overdose has been taken, indicates the likelihood of liver damage developing after 2 or 3 days. This test therefore helps the doctor decide on the need for antidotal treatment to minimise the risk of such damage occurring.

About Reference Intervals

Is there anything else I should know?

Taking as few as ten to twenty 500 milligram paracetamol tablets at once can cause serious, possibly fatal liver damage 2-4 days afterwards unless antidotal treatment is given within 8 hours. It is likely that there will be no symptoms of poisoning for 24-36 hours after taking the paracetamol even if a potentially fatal dose has been ingested. If paracetamol has been taken above the recommended dose you should seek medical help as soon as possible.

There is increased risk of liver injury with an overdose if persons are malnourished for any reason or alcoholic or if fasting for more than a day.

Common Questions

Is paracetamol dangerous if used appropriately?

Paracetamol is one of the safest, most effective drugs known if used at the recommended dose and dose interval.

Can paracetamol poisoning be treated at home?

No, if paracetamol poisoning is suspected, the patient should be taken to hospital immediately.

Last Review Date: January 9, 2023

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