Comparing Side Effects: What the Evidence Suggests
Wegovy and Mounjaro work on overlapping but distinct pathways. Wegovy acts on GLP-1 receptors, while Mounjaro acts on both GLP-1 and GIP receptors. Both mechanisms slow gastric emptying and reduce appetite — which is also why both can cause similar digestive side effects.
Commonly reported side effects with both medicines
- Nausea and vomiting
- Diarrhoea or constipation
- Indigestion and reflux
- Burping
- Fatigue and headache
- Injection-site reactions
Clinical trial populations, dose titration schedules, and individual biology all influence how side effects appear in practice, so direct comparisons between the two medicines are difficult to make in a simple way. Some people report fewer issues on one than the other — but the reverse is equally true for others. According to the electronic Medicines Compendium (eMC) product information, gastrointestinal events are listed among the most frequent adverse reactions for both tirzepatide and semaglutide.
Timing and pattern
For many people, side effects on either medicine tend to be most noticeable in the first few days after a dose increase and often ease as the body adjusts. This pattern — rather than the medicine itself — is frequently what people are experiencing when they describe one injection as feeling "easier" than another at a particular point in their journey.
For a detailed look at what people commonly experience on each medicine individually, see our guides on commonly reported Wegovy side effects and the broader Mounjaro side effects overview.
average weekly weight change in the first 16 weeks of Mounjaro & Wegovy use*
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Tracking Side Effects to Find Your Own Pattern
Because tolerability is so individual, the most useful thing you can do is track your own experience over time rather than relying on generalisations about one medicine versus another.
GLP Trackr's side-effect tracker lets you log symptoms — nausea, fatigue, digestive discomfort, and more — after each dose, so you can see whether they follow a predictable pattern across your weekly cycle. That kind of personal data can be genuinely useful to bring to your prescriber or doctor, especially if you are wondering whether a side effect is linked to a dose increase or settling down over time.
Alongside side-effect logging, the daily check-in feature captures your energy levels, mood, sleep, and food-noise score each morning — building a richer picture of how you are feeling week to week, not just on injection day. Some people find this broader view helps them distinguish a rough patch from a persistent concern worth raising with their healthcare team.
If you are experiencing side effects that feel severe, persistent, or worrying on either medicine, contact your healthcare professional promptly rather than waiting to see if they pass. GLP Trackr helps you record what you are experiencing so you can have a more informed conversation with your prescriber — it is not a substitute for their advice. Any concerns about which medicine suits you, or whether to continue, change, or stop, belong with your prescriber or doctor.
You may also find it helpful to read about less commonly discussed Mounjaro side effects as part of understanding your own experience.
Log your symptoms, spot your patterns, and walk into your next appointment with a clear picture of your journey. GLP Trackr is free to try for 7 days — available on the App Store and Google Play.
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Morning Check-In
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.
Injection Tracking
Log every dose with a single tap. Track your dose history, phase in your cycle, estimated medication levels, and upcoming injection dates — with reminders so you never miss a scheduled shot.
Hydration Reminders
Staying hydrated is especially important on GLP-1 medications. Set daily water targets, log intake throughout the day, and receive smart nudges when you're falling behind your goal.
Smart Meal Planning
Personalized meal plans built around your current dose phase and side effects. Every meal is GLP-1 optimized — high in protein, gentle on the stomach, and scaled to your reduced appetite.
Recipe Library
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Progress Analytics
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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Snap a photo of any meal and get a full nutrition breakdown in seconds — calories, protein, carbs, fat, and fibre. No searching. No manual logging. Just point, snap, and track.
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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 definitively easier to tolerate than the other. Both commonly cause gastrointestinal symptoms such as nausea, constipation, and diarrhoea. Individual experience varies widely, and which medicine suits you best is a decision for your prescriber or doctor.
No single injection can be said to have the fewest side effects for everyone. Tolerability depends on individual biology, dose stage, and other health factors. Your prescriber or doctor is the right person to help you weigh up which option suits your circumstances.
The side-effect profiles overlap considerably — both most commonly involve gastrointestinal effects like nausea, diarrhoea, and constipation. Some differences exist because the medicines act on slightly different receptors, but many people report similar experiences on either.
For many people, side effects are most noticeable in the first few days after a dose increase and often ease as the body adjusts over time. If symptoms feel severe or persistent at any stage, speak to your healthcare professional promptly.
GLP Trackr lets you log symptoms after each dose and track patterns over time. This record can be useful to share with your prescriber or doctor, especially around dose changes. The app is available free on the App Store and Google Play with a 7-day trial.