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How long does Calpol (paracetamol) last?
Medication3 June 2026·4 min read
Calpol (active ingredient: paracetamol) is the most commonly used fever and pain medicine for children in the UK. Understanding how it behaves over time helps you give the next dose at the right moment — neither too early, nor too late.
Indicative timings for paracetamol
- Onset: around 30 minutes after the dose
- Peak effect: 1 to 2 hours
- Duration: roughly 4–6 hours
- Minimum interval between doses: 4 hours (max 4 doses in 24 hours)
What that means in practice
If you give a dose at 8 p.m., it starts working around 8.30, is at its strongest around 9.30–10, and starts wearing off between 1 and 2 a.m. Knowing this helps you anticipate when the fever might come back, instead of being woken up by it.
Common mistakes
- Giving the next dose too early because "the fever is already back"
- Alternating paracetamol and ibuprofen without GP advice
- Estimating the dose by age rather than weight (for children)
In Fever Tracker, each dose of paracetamol draws an orange coverage band on the chart, so you can see at a glance until when the current dose is still working.
Important note. Fever Tracker content is for general information only and is not a substitute for advice from your GP or paediatrician. If you're worried, symptoms persist, or it's an emergency, always contact your doctor, paediatrician or your local NHS services.