How the Side-Effect Profiles of Mounjaro and Wegovy Compare
The overlap between the two medicines is substantial because both stimulate GLP-1 receptors, which slow gastric emptying and influence appetite. According to information in the electronic Medicines Compendium (eMC), the most frequently reported side effects for both tirzepatide and semaglutide at weight-management doses are gastrointestinal in nature.
Shared commonly-reported side effects
- Nausea and vomiting
- Diarrhoea and constipation
- Indigestion, bloating, and reflux
- Reduced appetite (often welcome, but can cause under-eating)
- Fatigue and headache, particularly around dose changes
- Injection-site reactions
Where the two medicines differ in mechanism
Mounjaro acts on both GIP and GLP-1 receptors — a dual mechanism that Wegovy, a GLP-1 receptor agonist only, does not share. Whether this translates into a meaningfully different side-effect experience varies between individuals and is not well established in direct head-to-head comparisons. Some people report that gastrointestinal symptoms feel different in character or timing between the two, but this is highly individual.
Dose and titration matter
Both medicines are typically started at a low dose and increased gradually under prescriber guidance. Side effects are most commonly reported around dose increases and often settle as the body adjusts. This pattern is similar for both medicines, which is one reason direct comparisons are difficult — the experience at any given dose stage may differ considerably from the experience at a higher maintenance dose.
If you are weighing up the two medicines in general terms, the broader Wegovy vs Mounjaro overview covers the key factual differences, and choosing between Mounjaro and Wegovy explores how that decision is typically made with a prescriber. For a look at how results compare alongside side effects, see which is more effective, Mounjaro or Wegovy.
average weekly weight change in the first 16 weeks of Mounjaro & Wegovy use*
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Tracking Side Effects Whichever Medicine You Are On
Because side effects on both Mounjaro and Wegovy tend to follow patterns — appearing after a dose increase, easing over days, or clustering around certain foods or habits — logging them consistently is one of the most practical things you can do.
GLP Trackr's side-effect tracker lets you record symptoms as they happen: what you felt, when, and how severe. Over time the app surfaces those patterns so you have something concrete to bring to your prescriber — whether you are reporting a difficult week, asking whether to adjust anything, or simply keeping a record as your dose changes. If you are also on Wegovy, the same tracking tools apply; the app supports both medicines. You might also find it useful to compare notes within the semaglutide medicine context if your prescriber has discussed options in that family.
Alongside side-effect logging, the daily check-in in GLP Trackr takes around 30 seconds each morning — capturing energy, mood, and sleep alongside your weight — which can help you spot whether a rough patch correlates with a dose day, a food choice, or something else entirely.
If any side effect is severe, persistent, or worrying — on either medicine — contact your healthcare professional promptly. Do not adjust your dose on your own; any change to your treatment is a decision for your prescriber, who knows your full history. Both medicines carry additional monitoring requirements, and suspected side effects can be reported to your national reporting scheme (such as the UK's Yellow Card scheme) as well as to your healthcare professional.
Ready to start logging? Download GLP Trackr on the App Store or Google Play and try it free for 7 days — your side-effect history will be waiting for you at your next appointment.
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Start every day with a 60-second wellness check-in. Log how you're feeling, track nausea, appetite, energy, and mood — giving you and your care team a complete picture of how your medication is working.
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Beautiful, easy-to-read charts show your weight loss trajectory, weekly nutrition trends, medication responses, and wellbeing scores over time — turning raw data into genuine insights.
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Log walks, workouts, and movement with activity targets that flex with your energy levels. On lower-energy dose days, gentler targets keep you moving without burning out.
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Frequently asked questions.
Neither medicine is established as definitively causing more side effects than the other. Both commonly cause gastrointestinal symptoms such as nausea, diarrhoea, and constipation. How individuals experience side effects varies widely; your prescriber is best placed to advise based on your health history.
The profiles overlap considerably — both commonly cause nausea, vomiting, diarrhoea, constipation, and indigestion. Mounjaro has a dual GIP and GLP-1 mechanism while Wegovy is GLP-1 only, which may influence individual experience, but the most reported effects are similar for both.
Side effects are most commonly reported around dose increases and often ease as the body adjusts over days or weeks. This pattern is similar for both Mounjaro and Wegovy. Always follow your prescriber's guidance on how your dose is managed.
Contact your healthcare professional promptly if a side effect is severe, persistent, or worrying. Do not adjust your dose yourself. You can also report side effects to your national pharmacovigilance scheme, such as the UK's Yellow Card scheme, as well as to your prescriber or doctor.
GLP Trackr lets you log symptoms, their timing, and severity for either medicine. Over time the app surfaces patterns you can discuss with your prescriber. It is a tracking tool, not a substitute for medical advice, but having a clear record can make those conversations more productive.