Is GLP-1 Safe? What to Know If You're Already Taking It

Because these medicines are prescription-only, their safety has been evaluated before they can be prescribed. Both tirzepatide and semaglutide act on appetite-regulating pathways in the body — tirzepatide on both GIP and GLP-1 receptors, semaglutide on GLP-1 receptors alone. You can read more about how these mechanisms work on our GLP-1 overview page.

Commonly reported side effects

The most frequently reported effects are gastrointestinal: nausea, constipation, diarrhoea, indigestion, and reflux. These are especially common when starting or after a dose is adjusted by a prescriber, and many people find they ease over time. Fatigue, headache, dizziness, and injection-site reactions are also commonly noted. According to NHS guidance, these effects are generally mild to moderate and tend to settle as the body adjusts.

Topics that require extra care

Certain situations call for a more careful conversation with your healthcare professional before and during treatment. These include a personal or family history of thyroid conditions, a history of pancreatitis or gallbladder problems, pregnancy or trying to conceive, and use of other medicines — particularly those used to manage blood sugar. Mental health and mood changes are also worth monitoring and discussing openly.

Both Mounjaro and Wegovy carry a black triangle (▼) designation in some countries, meaning they are subject to additional monitoring. Any side effects — especially unexpected or persistent ones — should be reported to your healthcare professional and to your national reporting scheme (such as the UK's Yellow Card scheme).

For a closer look at how Mounjaro specifically is used and monitored, see our page on GLP-1 and Mounjaro, or explore Mounjaro safety considerations in more detail.

One of the most practical things you can do while taking a GLP-1 medicine is keep a clear, consistent record of how you feel — not to self-diagnose, but so that when you speak to your prescriber or doctor, you have real detail to share rather than a vague impression.

GLP Trackr's side-effect tracker is built for exactly this. You can log symptoms as they happen — nausea, fatigue, digestive changes, injection-site reactions, mood — and the app surfaces patterns over time. If nausea is consistently worse the day after your injection, or fatigue clusters at a particular point in your week, that pattern becomes visible in a way it simply isn't when you're trying to recall it weeks later at an appointment.

The app also includes a doctor report feature that pulls your logged data into a clear summary — useful for making the most of a short appointment and ensuring nothing important gets missed. Beyond side-effect monitoring, you can use the daily check-in to note mood, energy, and sleep alongside your physical wellbeing, giving a fuller picture of how treatment is going for you overall.

GLP Trackr doesn't replace clinical oversight — it supports it. Any concern about whether a symptom is serious, whether your dose needs reviewing, or whether the medicine is right for you belongs with your prescriber, not an app. If a symptom is severe, persistent, or worrying, contact your healthcare professional promptly rather than waiting for your next scheduled appointment.

For a broader understanding of GLP-1 medicines and how people manage their treatment, visit our Mounjaro hub.

Want a clearer picture of how your body is responding week by week? GLP Trackr lets you log side effects, energy, mood and more — all in one place. Available free on the App Store and Google Play, with a 7-day trial to get started.