Available over the counter throughout the world, paracetamol is one of the safest and most reliable painkillers around. As we explore more in our main paracetamol guide, it?s suitable for use by all age groups, rarely produces side effects, and works effectively alongside most other forms of medication without causing issues.
That doesn?t mean that you can simply take as much as you?d like, though. Anything can be dangerous in excess, and paracetamol is no exception. In this article, we?re going to explain how much you should take (depending on various factors) and what you need to know about overdosing, including what the symptoms are and what can be done about it.
Why paracetamol is so popular
Paracetamol (or acetaminophen, also sold under the Tylenol brand) is so widely used because it?s extremely safe and generally effective at treating mild to moderate pain. It?s suitable for all age groups and rarely interacts negatively with other substances (medicinal or otherwise). It?s also extremely cheap and available everywhere as an over-the-counter medicine ? it can even be purchased from general stores (albeit with limitations on purchase amounts).
Getting paracetamol dosage right
As is also the case for every other medical treatment, paracetamol?s exceptional safety is dependent on its correct use. Many factors that can make other treatments dangerous do little to impact paracetamol, but something that does is its dosage level. Taking too little paracetamol will simply leave it ineffective, but taking too much can lead to illness or even death.
We touch upon this in our main piece, but here?s more detail about the suggested and maximum doses of paracetamol (or treatments containing paracetamol) for different age groups:
The recommended adult single dose of paracetamol is two standard 500 mg tablets. Research shows that the common threshold for liver damage to occur from a single paracetamol overdose is 15 gms (30 tablets) although standard hospital guidelines allow an extra safety margin and assume liver damage could occur at a single overdose of 24 standard tablets or 150 mg/kg body weight, whichever is the smaller.
How paracetamol can harm you
Paracetamol is mostly processed in the liver, and the process yields a toxic compound known as NAPQI. This isn?t an issue for normal doses because the liver naturally produces an antioxidant called glutathione which renders the NAPQI harmless. When you consume excess paracetamol, though, the liver can run out of glutathione and be unable to produce it sufficiently quickly to deal with the NAPQI, leaving it to cause liver damage (and possibly liver failure).
Additionally, because glutathione plays a key role in processing alcohol through neutralising the toxicity of ethanol, heavy drinking can sap the liver of its ability to deal with NAPQI, pushing a typically-safe dose of paracetamol into having the impact of an overdose. This is why you shouldn?t go close to the maximum dose of paracetamol for your size if you?ve been drinking.
Why would someone overdose on paracetamol?
Most people who overdose on paracetamol do so unintentionally. It?s possible to take 1000mg tablets while assuming that they?re 500mg tablets, for instance. The writing on the packaging is always perfectly clear, but if it?s dark or you?re not thinking clearly (often due to inebriation) then you can mix up two similar-looking packets in your haste.
Children can take too much paracetamol because they don?t understand what safe doses are, or even because they?re young enough to see eating random things as an agreeable pastime. This is the main reason why even the safest drugs must be kept away from kids: when they need pain relief, they must be given the correct doses by responsible adults.
Those who deliberately take more than intended, meanwhile, don?t usually expect it to be particularly dangerous. The commonality of the drug and its everyday-use level of safety can lead a user to incorrectly assume that it can?t hurt them. Since it?s best used to treat mild to moderate pain, someone with a greater level of pain can make the huge mistake of thinking that a massive dose of a mid-level painkiller will work flawlessly.
It?s also possible to overdose gradually, making it harder to spot. Someone constantly suffering from moderate pain can get into the habit of taking the maximum recommended dose of paracetamol at every opportunity, then slowly increase the frequency due to a lack of adverse reactions. When the overdose reaches the level of causing harm, they can mistake that harm for an escalation of the issue causing their pain, leading them to take even more paracetamol.
The overdose threshold may be lowered in a person taking certain prescription medicines, or a person who is an alcoholic or is seriously undernourished. If the overdose is spread over a period of time the threshold may be higher, as the initial paracetamol dose is effectively metabolised. (The recommended maximum dose in a 24 hour period is 4g or 8 tablets).
The other common explanation, sadly, is suicidal intent. Those who decide to end their lives can see paracetamol as a strong choice because it?s cheap, easy to acquire, and won?t generally cause the kind of suspicion that might get in the way. Most deaths from paracetamol overdoses (there are 130 each year in England and Wales) are deliberate. This is why it?s vital to do something if you think someone is at risk of self-harm, even if they seem to be acting normally.
What symptoms can indicate paracetamol overdose?
There are often no symptoms in the first 24 hours following overdose, although there may be mild nausea and vomiting. In a large overdose liver function deteriorates leading to jaundice, confusion, and loss of consciousness. Death is rare but when it occurs it is due to liver failure.
Even if the overdose is taken in one huge intake of tablets, the major effects (outside of stomach-based symptoms such as nausea) will take a while to appear as the NAPQI builds up and starts to damage the liver. When they arrive, they?ll be consistent with other liver issues: the user will likely experience pain around the liver area, jaundice (yellowing of the skin and the whites of the eye), and possibly a general disorientation stemming from a disorder called hepatic encephalopathy that develops when toxins missed by the liver spread to the brain.
There are other plausible symptoms, such as hypoglycemia (otherwise known as low blood sugar), kidney problems (including difficulty urinating), and hyperventilation. If it seems even possible that someone has taken an overdose of paracetamol, regardless of the extent of the overdose, it?s vital to get them medical care immediately. Their life may well be on the line.
How do medical professionals diagnose paracetamol overdose?
Noting the symptoms listed above is a strong indicator of liver issues, but a battery of blood tests will provide much more information. These tests can assess the following:
Paracetamol level. This test won?t reveal anything abnormal if the overdose has been gradual, but it?s useful even so, particularly when dealing with unresponsive patients.
Blood clotting. The liver plays a key role in blood clotting. This test gauges how long it takes blood to clot, giving one early indication of how well the liver is functioning.
General liver function. There are various tests that can gauge overall liver functionality, checking things like enzymes and blood waste products.
General kidney function. Kidney damage can often result from a paracetamol overdose. These tests determine how well kidneys are removing waste.
Blood acid levels. An overdose of paracetamol will quickly lead to increased blood acid levels, hinting at the extent of likely liver failure.
Blood sugar level. With hypoglycemia being a symptom of liver damage, frequent blood sugar tests can usefully reflect patient wellbeing.
Even with blood work back, further questioning may help to narrow down the diagnosis. Asking the patient directly if they?re capable of answering (or a friend or family member if they?re not), a doctor will pose various questions including these:
What drugs have they taken? When? In what form or forms? If the patient can?t remember or can?t (or won?t) answer, the onus will be on anyone with them to provide context clues. What drugs have they had access to? What painkillers do they tend to take? What do their normal doses look like? Could they have made a mistake?
Have they been drinking or seemed otherwise impaired? As mentioned earlier, heavy drinking inhibits the liver?s ability to safely process paracetamol. Along with other means of getting inebriated, it also impacts judgment, making it more likely for the drinker to get the wrong dose.
Do they have any notable recurring medical issues? Someone suspected of taking a paracetamol overdose may actually be reacting strongly to a typical dose due to an underlying liver problem. Knowing if the patient has been having other medical problems is extremely important for reaching a reasoned conclusion.
Have they been depressed or acting strangely? A suicidal person might well refuse to cooperate with efforts to help them. Understanding what the patient is going through is hugely significant as it can help the doctor get through to them.
What treatments are there for paracetamol overdose?
What should be done for the patient depends on the extent of the overdose and how quickly it was diagnosed. If their paracetamol level is sufficiently low and their overdose wasn?t gradual, they may require no treatment and simply need to rest until they recover. If their paracetamol level is dangerously high or they?ve taken a gradual overdose, they?ll need immediate treatment.
The typical treatment is intravenous N-acetylcysteine (NAC), which is a dietary supplement and antioxidant that serves to break down the NAPQI in the liver and any toxins that have spread around the body due to the liver?s problems. If the patient is extremely sick, they may need to be moved to intensive care where they can be resuscitated if necessary.
Treatment of a serious paracetamol overdose is mainly by administration of an antidote which can prevent the toxic effects of the overdose. This must be done early, ideally within 12 hours of the overdose although it can still be beneficial up to 24 hours or even later.
Treatment must be supervised in a hospital. It is important that if a paracetamol overdose is suspected, hospital treatment is sought without delay.
If the patient has taken a massive overdose and already sustained serious liver damage, there may be nothing that can be done to help them. Every patient who gets through their overdose, regardless of the conditions that led to it, will need to receive psychiatric evaluation to ensure that they?re not suicidal before they can be discharged. If further self-harm seems likely, they will be kept under observation until they can receive appropriate psychiatric care.
In England and Wales on average approximately 130 deaths per year can be directly attributed to paracetamol alone. In the vast majority of these cases the overdose is deliberate, and these deaths are returned as certain or probable suicides. In a small number of cases the overdose was intentional but the individual's expectation was not to cause death. Such deaths may be recorded as accidental.
When should you go to hospital after a paracetamol overdose?
Immediately. If you know that you?ve overdosed on paracetamol, every minute you wait will make your condition worse and raise the likelihood that you?ll suffer long-term effects. Call an ambulance if necessary and don?t do anything that might exacerbate the situation (such as drinking alcohol) while you?re waiting for assistance.
What is the lethal dose of paracetamol?
This question doesn?t have an easy answer because the amount that someone can tolerate depends on their weight, age, and liver condition. Due to this, it?s best to stop well short of the recommended maximum dose ? and if you?re in sufficient pain that you feel tempted to take more, speak to a medical professional about being prescribed something more potent.