Paracetamol: How Much Is Safe, and the Liver Risk
Paracetamol, sold here most commonly as Panadol, relieves pain and brings down fever. For a healthy adult weighing 50 kg or more the dose is 500 mg to 1 g at a time, no more often than every four hours, and never more than 4 g — that is eight 500 mg tablets — in any 24 hours. For children the dose is worked out by weight, about 15 mg for each kilogram, up to four doses in 24 hours, using the syringe or cup that comes with the bottle rather than a kitchen spoon. Taken within those limits it is one of the safest medicines available: it does not irritate the stomach, does not affect the platelets, and is the painkiller and fever medicine of choice in pregnancy and in dengue. Above those limits it damages the liver, and this is the fact that matters most on this page: after an overdose most people feel completely normal for the first 24 to 48 hours while liver injury is already underway, and the antidote works far better the earlier it is given. Anyone who has taken more than the daily maximum, in one go or spread across a day, needs to go to a hospital immediately, without waiting for symptoms. The commonest way people exceed the limit by accident is by taking a cold and flu preparation or a combination painkiller that already contains paracetamol on top of their ordinary tablets, so read every packet. People who weigh under 50 kg, who have liver disease, who drink heavily, who are very undernourished, or who take certain tuberculosis and epilepsy medicines may need a lower daily limit, which their doctor should set.
Health writers · Aslam Clinic
What paracetamol does, and what it does not
Paracetamol — acetaminophen in American labelling — relieves mild to moderate pain and lowers a raised temperature. It works mainly in the brain and spinal cord rather than at the site of the pain, which explains both its strengths and its limits. It is genuinely useful for headache, fever, toothache, period pain, muscle aches and the pain of and injury.
It is not an anti-inflammatory in any useful sense. Where the problem is swelling and — an acutely inflamed joint, for example — an such as ibuprofen may work better, which is a decision to make with a doctor rather than by trial and error. Paracetamol also does not thin the blood, does not affect , and does not erode the stomach lining, and those three absences are why it is the safe choice for people with , , ulcers, kidney problems, asthma triggered by aspirin, or those taking a blood thinner.
Nor is it a treatment for the illness underneath. Bringing down a temperature makes a person more comfortable and better able to drink; it does not shorten an infection, and a fever that keeps returning for more than three days needs a diagnosis rather than another dose.
Adult dose
| Who | Each dose | Minimum gap | Absolute maximum in 24 hours |
|---|---|---|---|
| Adult or child over 16, weighing 50 kg or more | 500 mg to 1 g (one or two 500 mg tablets) | 4 hours | 4 g — eight 500 mg tablets |
| Adult weighing under 50 kg | 15 mg for each kilogram of body weight | 4 hours | 60 mg per kilogram, and never more than 4 g |
| Chronic liver disease, heavy alcohol use, long-term undernutrition | Set by your doctor — often 500 mg at a time | 6 hours is often advised | Often reduced to about 2 g. Ask your own doctor for your limit. |
| On rifampicin, isoniazid, carbamazepine or phenytoin | Standard dose, but tell your doctor you take these | 4 hours | May be lowered. These medicines change how the liver handles paracetamol. |
Two practical points that prevent most accidental overdoses. First, if you are taking it around the clock, write down the time of each dose — people who are unwell, feverish or in pain lose track, and the second tablet taken because you cannot remember the first is how the total creeps up. Second, paracetamol should not be taken regularly for weeks without a review; if you need it every day for more than about three days for a new problem, or for longer than a fortnight for an old one, the problem needs looking at rather than medicating.
Children
Dose children by weight, not by age. The age bands printed on many local labels assume an average child, and a two-year-old in this country may weigh anywhere between about nine and sixteen kilograms — a difference large enough to matter. The standard is about 15 mg for each kilogram per dose, with at least four hours between doses and no more than four doses in any 24 hours.
| Child's weight | Dose each time | Volume of 120 mg/5 mL syrup | Maximum doses in 24 hours |
|---|---|---|---|
| 5 kg | 75 mg | 3 mL | 4 |
| 8 kg | 120 mg | 5 mL | 4 |
| 10 kg | 150 mg | 6 mL | 4 |
| 12 kg | 180 mg | 7.5 mL | 4 |
| 15 kg | 225 mg | 9 mL | 4 |
| 20 kg | 300 mg | 12.5 mL, or 6 mL of the 250 mg/5 mL forte | 4 |
| 25 kg | 375 mg | 7.5 mL of the 250 mg/5 mL forte | 4 |
| 30 kg | 450 mg | 9 mL of the 250 mg/5 mL forte | 4 |
| 40 kg or more | 500 mg | One 500 mg tablet | 4, and never more than 4 g |
Why the liver, and why it is silent
The liver breaks down most of a paracetamol dose harmlessly. A small fraction is converted into a reactive by-product, and the liver neutralises that using a substance called glutathione. In an overdose the glutathione runs out, the by-product accumulates, and it destroys liver cells directly.
That process takes time to show itself, which is the dangerous part. Hour by hour there may be nothing worse than nausea and vomiting, or nothing at all. Pain under the right ribs, , confusion and bleeding appear on the second or third day, by which point the are already badly deranged and options are narrower. The antidote, given as a drip in hospital, replaces what the glutathione was doing, and works best before the damage is established — which is why the emergency department wants to see the person at hour two, not at hour thirty.
Some people reach that point at lower doses than others: those weighing under 50 kg, people with existing liver disease, heavy or regular drinkers, anyone who is severely undernourished or has an eating disorder, people who have been fasting or vomiting for days, and those taking medicines that speed the liver's processing of drugs — rifampicin and isoniazid for tuberculosis, carbamazepine and phenytoin for epilepsy. If any of those describes you, ask your doctor what your own daily limit should be.
The hidden paracetamol problem
Paracetamol is in far more products than the box marked Panadol. Cold and flu tablets and sachets, night-time cold remedies, combination painkillers with caffeine or codeine, some migraine preparations and some period-pain products all contain it, often 500 mg per tablet, and they are sold without a prescription alongside plain paracetamol.
- Before taking any second product, read the ingredients on the pack and look for paracetamol or acetaminophen.
- Two 500 mg tablets plus a cold and flu sachet is 1.5 g in one go, and the day's total climbs quickly from there.
- Tell the pharmacist what you are already taking. Ask specifically whether the new item contains paracetamol.
- If a doctor prescribes a combination painkiller, stop the plain paracetamol unless you are told otherwise.
- Keep one product in the house rather than four half-finished boxes. It makes the arithmetic possible.
- Store tablets and syrup out of a child's reach and out of sight. Sweetened syrup is not perceived as medicine by a toddler.
Paracetamol or an anti-inflammatory?
| Question | Paracetamol | Anti-inflammatory (NSAID) |
|---|---|---|
| Fever and general aches | Effective, first choice | Also effective |
| Swollen, inflamed joint or injury | Helps with pain only | Usually more effective |
| Stomach lining | No irritation, safe in and ulcer disease | Can cause , ulcers and bleeding |
| Kidneys | Safe at normal doses in most kidney disease | Can worsen function, particularly with |
| Dengue and other bleeding-risk fevers | The correct choice | Avoid — increases bleeding risk when are falling |
| Pregnancy | First choice, lowest dose for the shortest time | Generally avoided, especially after 20 weeks |
| On a blood thinner | Preferred, though regular high doses can affect warfarin control | Generally avoided |
| Asthma | Safe for almost everyone | Triggers wheeze in a minority of people with |
| The main danger in overdose | Liver failure, and it is silent at first | Stomach bleeding and kidney injury |
Practical questions
- With or without food? Either. It does not need food to protect the stomach, though it may act slightly faster on an empty one.
- How quickly does it work? Usually within 30 to 60 minutes for tablets, sometimes sooner for syrup and dispersible forms.
- Missed a dose? Take it when you remember, unless the next one is nearly due. Never double up to catch up.
- Injections and drips? For someone who can swallow and keep tablets down, intravenous paracetamol offers no meaningful advantage over the same dose by mouth. Drips given routinely in clinics for ordinary fever add cost and an injection risk without adding benefit.
- Suppositories are useful for a vomiting child, but they count towards the daily total exactly like a tablet.
- Expiry and storage. Keep it below 30 degrees and out of the bathroom. Discard past the expiry date, and buy from a licensed pharmacy — counterfeit and substandard medicines are a real problem in the unregulated market.
- Alcohol. A regular heavy drinker should ask a doctor about a lower daily limit. An occasional drink with a normal dose is not the problem; sustained heavy drinking is.
When to see a doctor
- Immediately, at a hospital, for any suspected overdose — including a staggered one and including a person who feels well.
- Fever lasting more than three days in an adult, or that returns after settling.
- Fever in a baby under three months, at any temperature, or in any child who is drowsy, floppy, not drinking, breathing fast, or has a rash that does not fade when pressed.
- Pain that needs paracetamol every day for more than about two weeks. The cause needs identifying.
- , dark urine, pale stools, or pain under the right ribs while taking it.
- A rash, facial swelling or breathing difficulty after a dose — a genuine allergy to paracetamol is rare but does occur, and needs emergency care.
- If you have liver disease, are under 50 kg, drink heavily, or take tuberculosis or epilepsy medicines, ask for your own safe daily limit rather than assuming the standard one.
- For the fever itself rather than the medicine, see our articles on fever in adults and fever in children.
Common questions
Still not sure what to do?
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