How do I report a side effect to the Yellow Card scheme?
Report a suspected side effect online on the MHRA's Yellow Card website, in the free Yellow Card app, or by calling 0800 731 6789 (Monday to Friday, 9am to 5pm). Anyone can report one for Mounjaro (tirzepatide), Wegovy or Ozempic (semaglutide), or a pen they think is fake. You only need a suspicion, not proof.
What can you report to the Yellow Card scheme?
You can report a suspected side effect of any medicine, a medicine you think is fake, or a faulty one, with no proof needed.1
The MHRA, the UK medicines regulator, runs the scheme. It says "only a suspicion is needed".1 Its GLP‑1 guide asks anyone who suspects a reaction to a GLP‑1 medicine, or suspects a product isn't genuine, to report it.3 The UK Mounjaro leaflet says this includes side effects not listed in the leaflet.4 Patients and carers can report, as well as health professionals.1
How do you send a Yellow Card report?
There are four ways to report: the Yellow Card website, the Yellow Card app, a free phone line, or a paper form.1
- Online at yellowcard.mhra.gov.uk.2
- App: search "MHRA Yellow Card" in Google Play or the Apple App Store.4
- Phone 0800 731 6789, free, Monday to Friday, 9am to 5pm.1
- Paper: forms are at pharmacies and GP surgeries, and go back by Freepost.1,5
The UK Mounjaro leaflet also asks you to tell your doctor, pharmacist or nurse about any side effect.4
What should you put in a report?
Say what happened and when, list every medicine you were taking, and add your contact details so the MHRA can follow up.5
The Yellow Card Centre for Wales lists 5 parts to the form: the side effect, details of the person affected, all medicines taken, the GP's details (optional), and the reporter's details.5 For a GLP‑1, that means the brand, such as Mounjaro or Wegovy, and your dose. It says the information you give "will be kept safe, secure and confidential".5
What happens to your report?
The MHRA uses reports to spot new safety problems, and in 2025 it asked people taken to hospital with pancreatitis on a GLP‑1 to report.1,6
The MHRA says stomach effects such as nausea, vomiting and diarrhoea make up most of the Yellow Card reports it gets for GLP‑1 medicines.3 In June 2025 its Yellow Card Biobank asked people hospitalised with acute pancreatitis on a medicine like Ozempic or Mounjaro to report.6 The study asks for a saliva sample, to test whether genes affect who gets it.6 The MHRA's chief safety officer said every report is "extremely valuable", even outside the study.6
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Sources
- MHRA. The Yellow Card scheme: guidance for healthcare professionals, patients and the public (last updated 24 Jul 2025). gov.uk
- MHRA. Yellow Card: report a problem with a medicine or medical device (home page). yellowcard.mhra.gov.uk
- MHRA. GLP-1 medicines for weight loss and diabetes: what you need to know. Published 5 Jun 2025, updated 5 Feb 2026. gov.uk
- Eli Lilly. Mounjaro KwikPen (tirzepatide) UK patient information leaflet, last revised Aug 2026, sections 2, 3, 4 and 5. UK label. medicines.org.uk (emc)
- All Wales Therapeutics and Toxicology Centre (Yellow Card Centre Wales). Yellow Card reporting for patients, carers and the public. awttc.nhs.wales
- MHRA. If you take a GLP-1 medicine and have been hospitalised by acute pancreatitis, the Yellow Card Biobank wants to hear from you. Press release, 26 Jun 2025. gov.uk
- NHS. Stomach ache (page last reviewed 26 May 2023). nhs.uk
Last checked 12 Oct 2026 · Next review due 12 Oct 2027 · Report an error
How this answer was made. Written by the GLP Guidebook team from the sources above. It's general information, not medical advice. Talk to a qualified doctor before starting, stopping or changing any medicine. How we write