How GLP-1 Agonists Work and What They Do
GLP-1 (glucagon-like peptide-1) is a hormone released naturally after eating. GLP-1 agonist medications bind to GLP-1 receptors and amplify this signalling, producing effects that many people on these medicines notice in their day-to-day lives.
Key actions of a GLP-1 agonist
- Reduced appetite and "food noise": Stimulating GLP-1 receptors in the brain is associated with feeling fuller sooner and a quieting of persistent thoughts about food — commonly described by people on these medicines as reduced food noise.
- Slower gastric emptying: Food moves through the stomach more slowly, which contributes to a prolonged sense of fullness after meals. This effect is commonly reported to ease over time.
- Blood sugar regulation: GLP-1 agonists also play a role in glucose management, which is why medicines in this class have long been used in type 2 diabetes care, and why clinical supervision matters throughout treatment.
Is semaglutide a GLP-1 agonist?
Yes. Semaglutide — the active substance in Wegovy — is a GLP-1 receptor agonist. You can read more about semaglutide as a GLP-1 receptor agonist and how it acts on these pathways. For a broader look at the receptor mechanism itself, see our page on GLP-1 receptor agonists.
What about tirzepatide (Mounjaro)?
Tirzepatide is described as a dual agonist — it acts on both GLP-1 receptors and GIP (glucose-dependent insulinotropic polypeptide) receptors. This makes it a GLP-1 agonist and more; the combined action is part of what distinguishes it from single-receptor medicines. Learn more on our Mounjaro overview.
Commonly reported side effects of GLP-1 agonist drugs
The most frequently reported side effects of GLP-1 agonist medications relate to the gastrointestinal system — nausea, constipation, diarrhoea, indigestion, and reflux are all commonly noted, particularly in the early weeks or after a dose adjustment. Fatigue and headache are also reported by some people. These experiences vary considerably between individuals. According to NHS guidance, side effects should be discussed with your prescriber or doctor, especially if they are severe or persistent. For a broader look at the topic, visit our guide on GLP-1 and weight management.
average weekly weight change in the first 16 weeks of Mounjaro & Wegovy use*
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Tracking Your GLP-1 Journey with GLP Trackr
When you start a GLP-1 agonist, it can feel like a lot to keep track of — how you feel, what you eat, how your weight changes, and which side effects come and go. GLP Trackr is built specifically for people already on Mounjaro or Wegovy, and its side-effect tracker is one of the most practical tools on the app for this stage of your journey.
Log symptoms like nausea, fatigue, or digestive changes as they happen, and the app builds a picture of your patterns over time — useful context to bring to your next prescriber appointment rather than trying to recall how you felt three weeks ago. Alongside side-effect logging, the daily check-in captures mood, energy, food noise, and sleep in under a minute, so the quieting of food noise that many people notice on GLP-1 agonist meds becomes visible in your own data.
The weight and progress charts add another layer — tracking not just the number on the scale but the broader arc of your journey, week by week.
GLP Trackr helps you record what you're experiencing so you can discuss it with your prescriber — it is not a substitute for their advice. If any side effect is severe, persistent, or worrying, contact your healthcare professional promptly. Any decisions about your dose or treatment belong with your prescriber, who knows your full history.
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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.
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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.
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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.
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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.
A GLP-1 agonist is a medicine that mimics glucagon-like peptide-1, a hormone that helps regulate appetite and blood sugar. These prescription-only medicines are used to support weight management and include active substances such as semaglutide and tirzepatide.
Yes. Semaglutide, the active substance in Wegovy, is a GLP-1 receptor agonist. It binds to GLP-1 receptors to reduce appetite and slow gastric emptying. It is a prescription-only medicine and its suitability for any individual is decided by their prescriber or doctor.
Commonly reported side effects include nausea, constipation, diarrhoea, indigestion, fatigue, and headache — particularly in early weeks or after dose changes. Experiences vary between individuals. If side effects are severe or persistent, speak with your healthcare professional promptly.
A GLP-1 agonist acts on GLP-1 receptors only. Tirzepatide (Mounjaro) is a dual agonist — it acts on both GLP-1 and GIP receptors. Both are prescription-only medicines; the right choice for any person is a decision for their prescriber, not something to self-select.
GLP Trackr lets you log side effects, track weight, monitor food noise, and record daily check-ins — building a personal picture of your journey over time. This data can be useful to discuss with your prescriber. It is a tracking tool, not a medical service.