Acetaminophen (paracetamol)

Is acetaminophen safe?

Taken as the box says, yes. Acetaminophen, called paracetamol outside North America and sold as Tylenol, Panadol and Calpol, does not irritate the stomach, does not thin the blood and is not addictive. That is why doctors reach for it first in older people, in pregnancy and in children.

The catch is a small safety margin. The adult limit is 4,000 mg a day, and liver damage can start not far above it, especially in people who drink heavily, eat poorly or are already ill. Acetaminophen poisoning causes about half of all acute liver failure in the US. We score it 77: excellent on side effects, dependence and track record, but weak on overdose marginOverdose marginHow far a normal dose is from a harmful one. A wide margin means an accidental extra dose is unlikely to cause serious harm.More in the glossary.

How much is the maximum?

Source	Single dose	Daily maximum
FDA (all products combined)	Per product label	4,000 mg
NHS (500 mg tablets)	1 or 2 tablets, at least 4 hours apart	8 tablets (4,000 mg)
Tylenol Extra Strength 500 mg, US label	2 tablets every 6 hours	6 tablets (3,000 mg) unless a doctor directs

The NHS adds that people under 50 kg may need a lower dose. Children's doses go by age and weight, so use the syringe or cup in the pack, not a kitchen spoon.

The hidden acetaminophen problem

Most overdoses are not deliberate. In a US Acute Liver Failure Study Group series, 48% of acetaminophen liver failure cases were unintentional, often people in pain taking a bit more than allowed over several days, sometimes from two products at once.

Acetaminophen is in hundreds of products, and many do not say "Tylenol" on the front:

• night-time and daytime cold and flu remedies (NyQuil, DayQuil, Theraflu, Lemsip in the UK)
• headache products such as Excedrin, and sleep aids like Tylenol PM
• prescription painkillers such as Percocet (with oxycodone), Norco and Vicodin (with hydrocodone), and co-codamol in the UK

On US labels look for "acetaminophen" or "APAP" in the active ingredients; on UK and EU packs, "paracetamol". If a cold remedy contains it, do not take your usual painkiller on top. The FDA asked makers of prescription combinations in 2011 to cap acetaminophen at 325 mg per tablet, which leaves more room for error.

Overdose: why speed matters

Acetaminophen overdose is deceptive. For the first day there may be only nausea or nothing at all, while the liver is already under attack. An older US estimate puts the toll at about 56,000 emergency visits, 2,600 hospital stays and 458 deaths from liver failure a year. The antidote, acetylcysteine, prevents most liver damage if started within about 8 hours, so anyone who has taken too much should get help at once rather than wait for symptoms. The UK's limits on pack sizes, in force since 1998, were brought in to cut overdoses for the same reason.

Who should be careful

Talk to your doctor or pharmacist before using acetaminophen regularly if you:

• have liver disease, or drink three or more alcoholic drinks a day
• take warfarin, because regular doses can push up the INR
• weigh under 50 kg, are frail or eat very little
• need it for more than 10 days for pain or 3 days for fever (the US label's limits)

Pregnancy is a separate question. Acetaminophen is still the standard choice for pain and fever in pregnancy. In September 2025 the FDA began a label change about a possible link with autism and ADHD in children, while telling doctors a causal link has not been shown and that study results conflict. Its public page still says it has not found clear evidence of harm from appropriate use. If you are pregnant, discuss pain relief with your midwife or doctor rather than stopping or avoiding treatment for a high fever.

How to use it safely

• Keep a note of the time and dose when you are ill and taking several remedies.
• Use one acetaminophen-containing product at a time.
• Store it out of reach of children; liquid versions taste sweet.
• If you have taken too much, call Poison Control (1-800-222-1222 in the US) or NHS 111 even if you feel well.

How we scored it

Track record (97), dependence (97) and side effects at normal doses (88) are close to the top of our list. Overdose marginOverdose marginHow far a normal dose is from a harmful one. A wide margin means an accidental extra dose is unlikely to cause serious harm.More in the glossary (40) pulls the score down, because the gap to a toxic dose is small and acetaminophen is a leading cause of liver failure. For pain with inflammation, compare ibuprofen, which has the opposite profile: a wider overdose margin but more stomach and heart risk.