Side Effects of Wegovy and Mounjaro: What Commonly Happens and How to Track It

Both Wegovy and Mounjaro work on GLP-1 pathways in the body — pathways involved in appetite regulation and digestion. Mounjaro also acts on GIP receptors, making it a dual-action medicine. Because these pathways influence how quickly the stomach empties, gastrointestinal effects are the most frequently reported across both medicines.

Commonly reported gastrointestinal effects

• Nausea — very common, especially after dose changes; often described as peaking in the first day or two post-injection
• Vomiting — less universal but reported, particularly at higher doses
• Diarrhoea and constipation — both occur; some people experience one, some the other, and patterns can shift
• Indigestion, reflux, and burping — slower gastric emptying can contribute to these

Other commonly reported effects

• Fatigue and low energy — particularly in the days following an injection
• Headache and dizziness
• Injection-site reactions — redness, itching, or mild swelling at the injection site
• Mood and mental health changes — some people notice shifts in mood, low mood, or anxiety; see how mood and mental health effects are tracked for more on this
• Menstrual cycle changes — some people report period irregularities, likely connected to overall metabolic and weight changes rather than a direct drug effect, though always worth discussing with your prescriber

Less commonly discussed effects

Some people ask about effects on libido, liver, the pancreas, the heart, and cancer risk. For a closer look at less common and more serious reported side effects, including pancreatic and cardiovascular considerations, that page covers the topic in more depth. Any symptom that is severe, persistent, or feels medically significant should prompt a conversation with your healthcare professional promptly — do not wait for your next scheduled appointment.

Positive side effects people report

Not everything is difficult. Many people on Wegovy and Mounjaro describe meaningful reductions in "food noise" — the persistent mental preoccupation with food — alongside improved energy and mood as weight changes progress. These experiences vary widely and are not guaranteed, but they are genuinely reported.

What about no side effects?

Some people experience very few or no noticeable side effects, especially at lower doses. This is a normal variation and does not mean the medicine is not working. For a broader overview of the full side-effect picture, the complete Mounjaro and Wegovy side effects guide covers the topic comprehensively.

One of the most useful things you can do when experiencing side effects is keep a consistent record — not to self-diagnose, but so that you and your prescriber have real data to work with.

GLP Trackr's side-effect tracker lets you log symptoms as they happen — nausea, fatigue, digestive changes, mood shifts, and more — and surfaces patterns over time. If nausea always peaks on day two post-injection, or fatigue tends to cluster around dose changes, the app can show you that clearly rather than leaving you guessing. That kind of insight is genuinely useful to bring to a prescriber appointment.

The daily check-in also captures mood, energy, and sleep alongside any symptoms, which means you build a richer picture of how you are feeling across the whole week — not just on difficult days. If you want to explore how changes in energy or mood correlate with your injection schedule, the insights tools surface those connections automatically from your own data.

For anything relating to urinary symptoms specifically, tracking urinary side effects explains how to log those patterns effectively.

Important: GLP Trackr is a tracking tool, not a medical service. If any side effect is severe, persistent, or worrying — including serious abdominal pain, significant mood changes, or anything that feels medically urgent — contact your healthcare professional promptly. Any decisions about your dose or treatment should be made with your prescriber, not on your own. You can also report side effects to your national reporting scheme (such as the UK's Yellow Card scheme) — your prescriber or the patient information leaflet that came with your medicine can guide you on how to do this in your country.

Ready to start logging how you feel? GLP Trackr is free to try for 7 days — available on the App Store and Google Play. Start building a record that actually helps you at your next appointment.