Medicine Leaflets, Side Effects, and Interactions: Where to Find Reliable Information

When you open a new box of medicine, you’ll usually find a folded sheet of paper inside — the Patient Information Leaflet (PIL). These leaflets are important, but they can be hard to read because of the tiny print and the amount of information squeezed onto the page.

Patients often ask: Where does this information come from? What if I can’t read it? And how do I check for drug interactions as well as side effects?

Here’s what you need to know.

1. Where do leaflets come from?

• Written by the manufacturer – The drug company that makes the medicine is legally required to prepare the leaflet.

• Checked by regulators – In the UK, the MHRA (Medicines and Healthcare products Regulatory Agency) reviews and approves the leaflet before the medicine is sold. In Europe, this role is carried out by the EMA.

• Updated regularly – If new safety information comes to light (for example, through the Yellow Card reporting system), the leaflet must be revised and re-approved.

By law, leaflets must include:

• What the medicine is for.

• Who can and cannot take it.

• How to take it.

• Side effects and how common they are.

• Possible drug interactions.

• Storage instructions.

• How to report suspected side effects.

2. Why the text is so small

Because there’s so much information to fit into a tiny folded sheet, the print is often very small and difficult to read. For many patients, the leaflet in the box just isn’t practical.

3. Where to find more readable versions

If the leaflet is hard to read, you have better options:

• Electronic Medicines Compendium (eMC)

  • www.medicines.org.uk/emc

  • Up-to-date PILs and professional information for nearly all UK-licensed medicines.

  • Easy to zoom, search, and print in large text.

• BNF (British National Formulary)

  • bnf.nice.org.uk

  • Trusted source for doctors and pharmacists, but also useful for patients.

  • Lists side effects, cautions, and drug interactions clearly.

• NHS.uk

  • www.nhs.uk/medicines

  • Easy-to-read summaries of common medicines.

• Pharmacist

  • Can print a large-text version of the leaflet.

  • Can check for interactions with other medicines you take.

  • Some companies provide Braille, audio, or large-print versions on request.

4. Where to check drug interactions

Drug interactions are just as important as side effects, because they can make medicines stronger, weaker, or more dangerous.

• BNF online (bnf.nice.org.uk) – the best source in the UK, used by clinicians, with a clear section on interactions.

• eMC (SmPC section) – each drug’s Summary of Product Characteristics includes detailed interaction data.

• Pharmacist or GP – the safest and most personal check, since they know your full medication list.

• Hospital specialists – especially important if you are on antifungals, as these interact with many other medicines.

5. The bottom line

Medicine leaflets are carefully written, regulated documents — but the folded sheet in your box isn’t the only option, and it’s often not the easiest to use.

👉 You don’t have to struggle with tiny print. Reliable, readable versions are available online (eMC, BNF, NHS.uk), and your pharmacist can explain and print large-text copies.

👉 For drug interactions, never rely on random internet sources — use the BNF, eMC, or your healthcare team.

And if you’re ever unsure, ask your doctor or pharmacist before starting anything new, including over-the-counter medicines or supplements.