Encyclopedia entry

Patient Information Leaflet (PIL)

The Patient Information Leaflet is the folded paper leaflet inside every UK medicine box. It is the legally-required authoritative document on dosing, side effects, contraindications, missed-dose advice, and how to recognise a serious adverse reaction. PILs are produced by the marketing authorisation holder (the licence-holding manufacturer) and approved by the MHRA. They take precedence over web content, app content, and clinic advice.

What a PIL must include

• · What the medicine is and what it is used for (the licensed indication).
• · What you need to know before taking it (contraindications, warnings).
• · How to take it (dose, frequency, route, what to do for a missed dose).
• · Possible side effects, grouped by frequency (very common, common, uncommon, rare, very rare).
• · How to store the medicine.
• · What the medicine contains and what the packaging looks like.
• · How to report side effects via Yellow Card.

Why PIL trumps other sources

The PIL is the document the regulator approved as patient-facing safety information for that specific medication batch. Marketing copy, clinic advice, app notifications, and editorial content (including this site) are downstream of the PIL. When PIL guidance and a clinic\'s app advice conflict, the PIL is authoritative.

Where to find a PIL outside the box

Every UK-licensed medicine has its current PIL published at the electronic Medicines Compendium (emc.medicines.org.uk). Search by brand name (Mounjaro, Wegovy, Saxenda) or active ingredient. The same site holds the SmPC (the prescriber-facing equivalent).

Related: Yellow Card scheme · MHRA classification.