Health Risks of Mounjaro and Wegovy: What People on These Medicines Should Know

Both Mounjaro and Wegovy are GLP-1 receptor agonist medicines given as once-weekly injections. Their effects on appetite and digestion — which make them useful for weight management — also account for most of the commonly reported risks of weight-loss injections in this class.

Commonly reported side effects

• Gastrointestinal symptoms — nausea, vomiting, diarrhoea, constipation, indigestion, reflux, and burping are the most frequently reported effects, particularly after a dose is adjusted. Many people find these ease as their body adapts.
• Fatigue and dizziness — some people notice low energy or lightheadedness, especially in the early stages.
• Injection-site reactions — redness, itching, or mild bruising at the site of injection are occasionally reported.
• Headache — commonly noted, especially early in treatment.

Less common but more serious risks

According to information aligned with the electronic Medicines Compendium (eMC), there are rarer but more significant risks that warrant medical attention. These include signs of pancreatitis (severe, persistent abdominal pain that may spread to the back), gallbladder problems (such as gallstones), and heart rate changes. People with a personal or family history of certain thyroid conditions should discuss this specifically with their prescriber before starting treatment.

Both medicines carry a black triangle (▼) designation in the UK, meaning they are subject to additional monitoring. Any suspected side effect should be reported to your national reporting scheme (such as the UK's Yellow Card scheme) and discussed with your healthcare professional.

For a closer look at the specific risk profile of tirzepatide, see the risks of Mounjaro explained, or explore common Mounjaro risks and how to manage them with your prescriber's guidance.

One of the most practical things you can do while taking Mounjaro or Wegovy is keep a clear, dated record of any symptoms you experience — not to self-diagnose, but so you have useful, specific information ready when you speak to your prescriber or doctor.

GLP Trackr's side-effect tracking feature is built exactly for this. You can log symptoms as they occur — nausea, fatigue, digestive discomfort, injection-site reactions, mood changes — and the app builds a timeline that shows patterns over days and weeks. Spotting that symptoms cluster in the 24 hours after an injection, for example, is the kind of insight that makes a prescriber appointment far more productive.

Alongside side-effect logging, the daily check-in captures energy levels, mood, sleep, and how you're feeling overall, giving you a fuller picture to share. If your prescriber asks how you've been feeling over the past month, you'll have a real record rather than a rough estimate.

If any symptom is severe, persistent, or worrying — especially abdominal pain, chest pain, or anything that feels out of the ordinary — contact your healthcare professional promptly rather than waiting for your next scheduled appointment. GLP Trackr helps you record what's happening; it is not a substitute for clinical care, and any concern about your health risks or side effects belongs with your prescriber, who knows your full history.

For a broader view of the science behind how these medicines work and what to expect, the Mounjaro overview hub is a good starting point. You can also read about the reported health benefits of Mounjaro for a balanced picture alongside the risks.

Start logging your symptoms and building a record you can actually use — GLP Trackr is free to try for 7 days on the App Store and Google Play.