Side effects & safety
What to expect, how long it lasts, and how to manage it — plus safe storage and when to seek help.
Most side effects of GLP-1 weight-loss medicines are digestive — nausea, reflux, constipation or diarrhoea — and most settle within a few weeks as the body adjusts. They are usually worst in the days after a dose increase. A small number of symptoms are not normal at any stage: severe or persistent abdominal pain, repeated vomiting, signs of dehydration, or a severe allergic reaction. Those mean stopping the medicine and seeking medical advice the same day.
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Read article →Common questions
How long do Mounjaro and Wegovy side effects last?
Digestive side effects are usually worst in the first few days after starting or after a dose increase, and commonly ease over two to four weeks at a steady dose. If a symptom is still troubling you after a month at the same dose, or it is getting worse rather than better, speak to your prescriber before the next increase rather than pushing on.
Which side effects mean I should stop and seek help?
Severe or persistent abdominal pain, especially pain that radiates to the back, can indicate pancreatitis and needs urgent assessment. Repeated vomiting, an inability to keep fluids down, or swelling of the face, lips or throat also need same-day medical advice. In an emergency call 999; otherwise call NHS 111 or your prescriber.
Can I reduce side effects by going up more slowly?
Often, yes. Staying at your current dose for an extra cycle before increasing is a recognised way to let symptoms settle, and a prescriber can agree that with you. It may slow progress slightly but it is usually better tolerated than pushing through. Never change your dose without telling your prescriber.
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