Paracetamol or Ibuprofen: How They Differ and Where the Limits Are

Two boxes in the cabinet that look interchangeable — and are not. Paracetamol lowers fever and eases pain and, in excess, damages the liver. Ibuprofen is an NSAID: it also works on inflammation, and its price is paid by the stomach, the kidneys and the heart. Which one, how much and for how long depends on your health, your weight and the country whose leaflet is in the box. Doses for children are on a separate page: paracetamol and ibuprofen doses for children.

When to see a doctor

Right away: trouble breathing, seizures, a rash that does not fade under a pressed glass, confusion or a person who cannot be woken, blue lips (CDC, US; NHS, UK). Also right away, even if you feel fine: any suspicion of an extra dose of paracetamol — two products contained it, or you lost count. An overdose shows no symptoms for hours, and the antidote works best early (NHS, UK). And: black or bloody stools, vomiting blood or faintness while taking ibuprofen; swelling of the face or throat after a tablet.

The same day: fever longer than four days (CDC, US) or three (NHS, UK); pain not controlled after three days.

Routinely: if you take either drug more than a few days a month; if you have liver, kidney, heart or stomach disease; if you take warfarin or another anticoagulant — choose the drug with a doctor. The full three tiers for a cold, with emergency numbers by country, are on the first signs of a cold.

What is happening

Paracetamol is gentle at the right dose and dangerous just above it, because the liver's capacity to neutralize it runs out. That is why every rule is about the sum: no more than one paracetamol-containing product at a time, and three or more alcoholic drinks a day on top can cause severe liver damage (FDA, US). The NHS (UK) adds a lower dose if you weigh under 50 kg, and a check with a doctor if you have liver or kidney disease, drink heavily or take warfarin.

Ibuprofen blocks the same enzymes that protect the stomach lining and keep blood flowing through the kidneys. The FDA (US) strengthened its warning in 2015: NSAIDs raise the risk of heart attack and stroke, more so at higher doses, with longer use and in people with heart disease, and they raise the risk of heart failure. Ibuprofen can also blunt the protective effect of low-dose aspirin; the FDA asks you to discuss timing with a doctor. The NHS (UK) lists who should not take it, or should ask first: a stomach ulcer now or ever; heart, liver or kidney disease; asthma; pregnancy or trying for one; an allergy to aspirin or NSAIDs; bleeding problems; and anyone on warfarin, steroids, antidepressants or blood pressure medicines. Never together with another NSAID.

Pregnancy. From week 20, no NSAIDs without a doctor: low amniotic fluid and fetal kidney injury (FDA, US; the Russian ibuprofen leaflet says the same). Paracetamol is the usual choice in pregnancy and breastfeeding (NHS, UK).

What to do

Paracetamol, adults. UK: 500 mg tablets, one or two per dose, at least four hours apart, no more than eight tablets (4 g) in 24 hours, no longer than three days without a doctor. US: no more than 4,000 mg in 24 hours from age 12; single dose and duration by the product's Drug Facts. Russia: 500 mg per dose, at most 1 g at a time, at least four hours apart, up to four times a day, at most 4 g a day; without a doctor, three days for fever and five for pain; leaflets tie this regimen to body weight (over 40 kg in some, over 60 kg in others) — below that, follow your own leaflet and ask.

Ibuprofen, adults. UK: 200 mg tablets, one or two up to three times a day, at most six (1,200 mg) in 24 hours, at least four hours apart, ideally with or after food, no longer than ten days without a doctor. Russia (Nurofen 200 mg leaflet): 200 mg up to three or four times a day, or 400 mg up to three times, at least six hours apart, at most 1,200 mg a day; if symptoms persist after two or three days, stop and see a doctor; contraindicated with an active ulcer or bleeding, severe heart failure, bleeding disorders, the "aspirin triad" (asthma with nasal polyps and aspirin intolerance), and from week 20 of pregnancy. US: by the product's Drug Facts.

Together? Adults in the UK may take paracetamol and ibuprofen at the same time if needed (NHS), each within its own limits.

Aspirin is an NSAID too, with its own limits: in Russia the 500 mg leaflet gives 0.5–1 g per dose, at most 1 g at a time, at least four hours apart, at most 3 g (six tablets) a day, three days for fever and seven for pain without a doctor, and excludes children under 15 with viral infections; the UK says no aspirin under 16 and the US label warns for children and teenagers with chickenpox or flu-like symptoms — Reye's syndrome. Not in the first or third trimester, nor while breastfeeding (Russian leaflet).

When this is not the case

During vomiting, diarrhea or fever with little drinking, ibuprofen is a bad idea for anyone whose kidneys are already under strain: NHS Scotland's "sick day rules" ask people on blood pressure medicines, diuretics or metformin to check whether to pause them, and NSAIDs are on that list. And the numbers above are for adults in the leaflet's weight range: an adult under 40–60 kg, an older person on several medicines, anyone on chemotherapy — the leaflet and the doctor decide. Related: measuring liquid medicines, dehydration and oral rehydration, what helps with a cold, and why a brand name tells you none of this — the active ingredient.

Sources

Checked: September 7, 2026