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Foundayo side effects
About this page. Written by the GLPInfo editorial team with AI assistance from the official sources listed at the end, and approved by the site owner before publication. It has not been reviewed by a named clinician. Published 27 Aug 2026 · last updated 27 Aug 2026 · next scheduled review 27 Nov 2026.
This page is information, not medical advice. It never tells you which medicine, dose or format is right for you: those decisions sit with you and a qualified prescriber. Spotted an error? Tell us and we'll fix it fast.
This page summarises how the patient information leaflet categorises Foundayo's side effects. It is deliberately unsoftened: the leaflet in your pack is the authority, your prescriber assesses your personal risk, and Report suspected side effects through the MHRA Yellow Card scheme.
Common effects
The most commonly reported effects, per the product information and the ATTAIN-1 trial, are gastrointestinal: nausea, constipation, diarrhoea, vomiting, indigestion and abdominal pain, along with headache, bloating, belching, heartburn, wind, tiredness and hair loss. As with the other GLP-1 medicines they cluster around dose increases, which is why the ladder moves in steps of at least 30 days.
Serious risks
Serious risks listed in the product information include acute pancreatitis, severe gastrointestinal effects leading to dehydration, and low blood sugar in combination with certain diabetes medicines. Severe, persistent abdominal pain needs urgent medical attention. Foundayo is new to the UK (licensed August 2026): its UK safety experience is accumulating, which makes Yellow Card reporting of suspected effects genuinely useful.
Worth knowing
Not for use in pregnancy. Because the medicine is new, the leaflet in the pack is the current authority and may be updated as UK experience grows; check it with each new pack rather than assuming it is unchanged.
Managing the common effects
Practical, NHS-guidance-level measures for nausea, constipation and dehydration, plus the red flags that mean stop self-managing and call, are collected in one place: managing GLP-1 side effects. Always tell your prescriber what you are experiencing; dose timing and step-ups are their levers, not yours.
Related: what is Foundayo? · how to take Foundayo · dose schedule
Frequently asked questions
Do Foundayo side effects go away?
The common gastrointestinal effects are typically worst after starting or increasing a dose and ease as the body adjusts, which is exactly why doses climb slowly. Effects that are severe, persistent or worrying belong with your prescriber, not with waiting. Practical self-care measures are covered in managing GLP-1 side effects.
When should I seek urgent help?
Severe persistent abdominal pain (with or without vomiting), signs of an allergic reaction such as swelling of the face or throat or difficulty breathing, or signs of serious dehydration all need urgent medical attention: 999 or A&E for the emergencies, NHS 111 when unsure.
Should I report side effects even if they are listed?
Yes. Reporting through the MHRA Yellow Card scheme strengthens the safety picture for everyone, and reporting something does not require certainty that the medicine caused it.