Paracetamol: uses, safe limits and what to do if you take too much

Paracetamol is a simple painkiller that also brings down a high temperature. On its NHS page the uses named are headaches, joint swelling and stiffness, the symptoms of a cold or flu including fever, toothache and a sore throat. The NHS page does not set out how it works, so this guide does not either.

It is not an anti-inflammatory in the way ibuprofen is, which is why it sits in a different group from the NSAIDs. For many people with everyday pain that is a reason to try it first, because the NHS notes that ibuprofen can cause more side effects than paracetamol.

Adult paracetamol comes as tablets and capsules (including dissolvable ones), liquid suspension and suppositories. How you use it depends on the type, and the NHS says that someone weighing under 50kg may need a lower dose, so check the leaflet rather than assuming.

The figures below are those the NHS gives for common adult products. They are limits, not targets, and a prescriber may give different directions.

• 500mg tablets or capsules: 1 or 2 per dose, at least 4 hours between doses, a maximum of 8 in 24 hours.

• 1g tablets (sometimes prescribed or supplied by a pharmacist): one at a time, no more than 4 in 24 hours.

• 250mg in 5ml liquid: 10ml to 20ml a dose, no more than 4 doses in 24 hours.

• 500mg in 5ml liquid: 5ml to 10ml a dose, no more than 4 times in 24 hours.

• Suppositories: the same 24-hour ceilings apply, according to whether they contain 500mg or 1g.

The commonest way people overshoot is not by swallowing extra tablets but by combining products. Many cold and flu remedies already contain paracetamol, and the NHS specifically warns against taking these alongside plain paracetamol because the total can become dangerous. Reading the active-ingredient panel on every product is the simple safeguard.

An extra dose is unlikely to cause problems, according to the NHS, but taking more than the packet or leaflet allows can sometimes damage the liver, so it advises getting help from NHS 111. If you are told to go to A&E, do not drive; ask someone else or call 999. Take the packet and any other medicines with you.

Paracetamol very rarely causes side effects when it is taken correctly. The rare serious ones the NHS describes are an allergic reaction (swollen throat or tongue, raised itchy rash, difficulty breathing), liver problems with nausea or yellowing of the skin or whites of the eyes, and blood-cell problems that show up as easy bruising and nosebleeds. If you think you are having a serious side effect, the NHS says to call 111.

It may not be suitable if you have had an allergic reaction to it, if you have a kidney or liver condition, or if you are dependent on alcohol or binge drink. The leaflet and a pharmacist can say whether it is right for you.

In pregnancy the NHS calls paracetamol usually the best painkiller to use and says it is commonly taken and does not harm the baby. For breastfeeding it gives the same verdict, while noting that anyone worried about their baby should speak to a healthcare professional.

The NHS lists medicines that may not mix well with paracetamol: other paracetamol-containing products, the anti-sickness medicines metoclopramide and domperidone, blood thinners such as warfarin, and the antibiotic flucloxacillin. Adults can take paracetamol and ibuprofen together if needed, but the NHS suggests trying each on its own first, using the lowest dose that works and stopping when the pain has gone.

If pain is still there after three days of paracetamol, that is the point at which the NHS wants a doctor involved rather than a longer run of tablets. Persistent pain has causes worth looking for, and stronger or different medicines are decisions for a prescriber.

Some people move to ibuprofen or another anti-inflammatory for muscle and joint pain, or to paracetamol combined with a codeine-type ingredient on prescription or from a pharmacist for a short period. Those have their own cautions, covered in the linked guides.