Side effects and when to get help
Most side effects of GLP-1 medicines are stomach-related and ease over a few weeks. A few need urgent care. Know which is which.
Get help now
Call 999 if you have severe difficulty breathing, collapse, or swelling of the face, lips or throat.
Get urgent advice the same day for severe stomach pain that will not go away, especially if it spreads to your back or comes with vomiting. The same applies if you cannot keep fluids down, pass hardly any urine, or have sudden changes in your sight.
For anything else urgent, call NHS 111 or use 111 online. Outside the UK, use the local emergency number.
NHS: when to call 999Safety guides
Blood tests before and during GLP-1 treatment
Why a prescriber may ask for blood tests before or during GLP-1 treatment, what the tests show and who should explain and act on your results.
3 min readSafetyHydration and dehydration on GLP-1 treatment
Spot dehydration on GLP-1 treatment and know when vomiting, low fluid intake or passing little urine needs urgent medical advice.
3 min readSafetyNot eating enough on a GLP-1 medicine
When appetite suppression turns into under-eating, why malnutrition happens at any body size and how to ask your prescriber for a review.
3 min readSafetyGLP-1 medicines and eating disorders
Eating-disorder concerns at any body size on GLP-1 medicines: what to tell your prescriber and why appetite treatment cannot replace specialist care.
3 min readSafetyFatigue and low energy on GLP-1 medicines
Tiredness on a GLP-1 medicine: common causes, glucose and hydration checks, how to describe fatigue to your clinician and symptoms that need urgent help.
3 min readSafetyPregnancy planning and GLP-1 medicines
When to stop semaglutide, tirzepatide or orforglipron before trying to conceive, plus contraception and diabetes care while you plan a pregnancy.
3 min readSafetyContraception and GLP-1 medicines
Contraception rules for tirzepatide and Foundayo differ. See when to add a barrier method and what to do after vomiting or diarrhoea on the pill.
3 min readSafetyBreastfeeding and GLP-1 medicines
UK labels for Mounjaro, oral Wegovy and Foundayo give different breastfeeding advice. Find out what to check and which decisions need your clinical team.
3 min readSafetySurgery, sedation and GLP-1 medicines
Taking a GLP-1 medicine before surgery or sedation? What to tell the anaesthetic team, why aspiration matters and how to plan fasting and restarting.
3 min readSafetyUrgent symptoms on GLP-1 medicines: when to get help
Serious symptoms on a GLP-1 medicine, from severe stomach pain to dehydration, and when to call 999, NHS 111 or an urgent GP in the UK.
3 min readSafetyHow to report a side effect with Yellow Card
Report a suspected medicine reaction or quality problem through the UK Yellow Card scheme. What to include and what a report can and cannot show.
3 min readSafetyHow to check a UK online pharmacy before you order
Check a UK online pharmacy's registration, identity, prescribing checks and aftercare before you order a GLP-1 medicine. Logos and reviews are not enough.
3 min readSafetyCold-chain delivery of GLP-1 medicines
How to store temperature-sensitive GLP-1 pens and what to ask the pharmacy when a delivery arrives late, damaged or warm.
3 min readSafetyCounterfeit GLP-1 medicines: how to spot the risk
Fake GLP-1 pens can contain the wrong dose or even insulin. Why packaging cannot prove a product is genuine and what to do if a supplier seems suspicious.
3 min readSafetyResearch peptides and why they are unsafe to inject
A research-use label or purity certificate does not make a peptide safe to inject. How clinical trials differ from buying a vial online.
3 min readSafetyCounting pen clicks for off-label GLP-1 doses
Pen clicks are no universal dose measure. How off-label prescribing differs from changing your own dose, and what to confirm before you inject.
3 min readSafetyLeftover pen liquid and the so-called fifth dose
Liquid left in a GLP-1 pen is no extra prescribed dose. The risks of drawing it out, and how to raise cost or supply problems with your prescriber.
3 min readMounjaroMounjaro abdominal pain and pancreatitis warning signs
Severe, lasting tummy pain on Mounjaro needs urgent care. Learn the pancreatitis warning signs, what to tell doctors and how assessment works.
3 min readMounjaroMounjaro, dehydration and kidney problems
Vomiting or diarrhoea on Mounjaro can dehydrate you and harm kidney function. See the warning signs, how to replace fluid and when to get help.
3 min readWegovy injectionVomiting on Wegovy: when to get urgent help
Vomiting on Wegovy: how to stay hydrated, which warning signs need urgent help, why you never repeat an injection and how to plan your next dose.
3 min readWegovy injectionWegovy and pancreatitis: symptoms, risk and urgent action
Pancreatitis warning signs on Wegovy, what the MHRA safety update in January 2026 said and why severe tummy pain needs urgent assessment.
3 min readWegovy injectionWegovy, dehydration and kidney function
How vomiting or diarrhoea on Wegovy can dehydrate you and affect your kidneys, with practical steps, advice on other medicines and urgent warning signs.
3 min readWegovy injectionWegovy and eyesight: NAION, diabetes and urgent symptoms
The rare semaglutide link with NAION, how it differs from diabetic retinopathy and when sudden changes in your eyesight need urgent care.
3 min read