Paracetamol is used to relieve mild to moderate pain and reduce fever. It is one of the most widely taken medications in the world, available over the counter in nearly every pharmacy, and it works for a broad range of everyday complaints: headaches, toothaches, sore throats, cold and flu symptoms, and joint stiffness. Unlike ibuprofen and aspirin, paracetamol is not an anti-inflammatory, which means it won’t reduce swelling but is gentler on the stomach.
Common Uses
The NHS lists paracetamol’s primary uses as treating headaches, toothache, sore throat, joint swelling and stiffness, and the fever and body aches that come with colds and flu. In practice, most people reach for it whenever they have a mild pain that doesn’t need something stronger. It’s also frequently recommended after minor surgery or dental procedures when inflammation isn’t the main concern.
Because it doesn’t irritate the stomach lining the way ibuprofen can, paracetamol is often the first choice for people who are prone to acid reflux, stomach ulcers, or gastrointestinal bleeding. It’s also the preferred painkiller for people who can’t take anti-inflammatory drugs due to kidney issues or asthma triggered by NSAIDs.
How It Relieves Pain
For decades, scientists assumed paracetamol worked the same way as ibuprofen, by blocking the enzymes that produce pain-signaling chemicals called prostaglandins. That turns out to be only a small part of the story. Current research published in Frontiers in Pharmacology shows that paracetamol is converted in the body into a compound called AM404, which crosses into the brain and spinal cord and acts on pain receptors there directly. This is why paracetamol is sometimes described as a “central” painkiller: its main effects happen in the brain and spinal cord rather than at the site of injury.
AM404 interacts with receptors involved in the body’s own pain-dampening systems, including pathways shared with the endocannabinoid system and natural opioid pathways. Paracetamol also boosts serotonin activity in parts of the brain involved in pain processing. The combined effect is a broad, mild suppression of pain signals. This central mechanism explains why paracetamol eases pain effectively but does almost nothing for the redness, heat, and swelling of inflammation.
How It Lowers Fever
When you’re fighting an infection, your brain’s temperature-control center raises your body’s set point, producing fever. Paracetamol resets that thermostat by blocking prostaglandin production specifically inside the central nervous system. The result is that your body stops generating extra heat and begins cooling itself through sweating and increased blood flow to the skin. It won’t lower a normal body temperature, only an elevated one.
How Quickly It Works
Standard oral tablets typically begin relieving pain within 30 to 60 minutes. Intravenous paracetamol, used in hospitals, starts working within five to ten minutes. Regardless of the form, peak pain relief arrives about one hour after the dose, and the effect lasts four to six hours. This is why dosing is usually spaced at least four hours apart.
Paracetamol vs. Ibuprofen
The key difference is inflammation. Ibuprofen is an anti-inflammatory drug, so it reduces swelling, redness, and the pain that comes from inflamed tissue. Paracetamol is not. For a sprained ankle or a swollen knee, ibuprofen will generally do more. For a tension headache, a sore throat, or a fever, paracetamol works just as well and carries fewer stomach risks.
Ibuprofen can cause stomach ulcers, gastrointestinal bleeding, and long-term kidney problems, particularly in people who use it frequently. Paracetamol avoids those issues entirely, which is why it is often recommended for older adults, people on blood thinners, and anyone with a history of stomach trouble. The trade-off is that paracetamol carries its own risk: liver damage, particularly in overdose or with heavy alcohol use.
Liver Risk and Overdose
Paracetamol is safe at recommended doses, but the margin between a therapeutic dose and a dangerous one is narrower than many people realize. Your liver processes paracetamol by attaching it to a protective molecule called glutathione, which neutralizes a toxic byproduct. At normal doses, there’s plenty of glutathione to go around. In overdose, glutathione runs out, and the toxic byproduct accumulates, directly damaging liver cells. Paracetamol overdose is the most common cause of acute liver injury worldwide.
The risk increases significantly in three situations: taking more than the recommended amount in 24 hours, combining paracetamol with alcohol, and not realizing that other medications (cold and flu remedies, some prescription painkillers) already contain paracetamol. The American College of Rheumatology recommends avoiding paracetamol entirely in people with chronic alcohol abuse and using it cautiously in anyone with existing liver disease. Even in heavy drinkers who take the correct dose, the liver’s reduced glutathione reserves and altered metabolism can tip the balance toward toxicity.
Use During Pregnancy
Paracetamol remains the safest over-the-counter pain and fever medication available during pregnancy. Both aspirin and ibuprofen have well-documented harmful effects on fetal development, making them poor alternatives. That said, recent studies have raised questions about a possible link between prolonged paracetamol use throughout pregnancy and a slightly increased risk of neurodevelopmental conditions like ADHD in children. The FDA has noted this association but emphasizes that a direct cause-and-effect relationship has not been established, and conflicting studies exist.
The practical takeaway: short-term use for significant pain or high fever is still considered appropriate in pregnancy. Routine use for low-grade fevers that don’t genuinely need medication is worth reconsidering, since most mild fevers in pregnant women resolve on their own.
Use in Children
Liquid paracetamol can be given to most children from two months of age, provided the baby weighs over 4 kg and was born after 37 weeks. It’s the go-to medication for childhood fevers and teething pain. Dosing for children is based on age and sometimes weight, and it varies between brands, so always check the packaging rather than guessing. Children’s formulations come as a liquid suspension, making them easier to swallow and measure accurately.
The same liver risk that applies to adults applies to children. Giving more than the recommended amount, or accidentally doubling up because a child is also taking a cough syrup that contains paracetamol, can cause serious harm. Keeping track of every dose and checking ingredient lists on combination medicines is essential.