GIP and GLP-1: What These Receptors Actually Do
Mounjaro is classified as a dual GIP and GLP-1 receptor agonist. To understand what that means in practice, it helps to know what each pathway normally does in the body.
The GLP-1 pathway
GLP-1 (glucagon-like peptide-1) is a hormone released naturally by the gut after eating. It signals to the brain that you have eaten, slows the rate at which the stomach empties, and helps regulate blood sugar levels. Medicines that act on this receptor — including both Mounjaro and medicines that work via the GLP-1 pathway alone — mimic and amplify these effects. For a closer look at how GLP-1 agonism works in general, see our overview of the GLP-1 receptor agonist mechanism of action.
The GIP pathway
GIP (glucose-dependent insulinotropic polypeptide) is a second gut hormone that also influences appetite regulation, fat metabolism, and the body's response to food. Tirzepatide's dual action on both GIP and GLP-1 receptors is a distinctive feature of Mounjaro specifically — you can read more about how GLP-1 receptor activation works as part of this broader picture.
What this means in practice
Many people prescribed Mounjaro report a noticeable reduction in appetite and what is often described as "food noise" — the persistent mental preoccupation with food. Slower gastric emptying (the stomach taking longer to move food into the intestine) is commonly reported too, which contributes to a prolonged sense of fullness. It is worth noting that gastric-emptying effects can lessen over time for some people. These are commonly observed patterns; individual experience varies, and the medicine affects people differently depending on their own physiology and other factors.
According to information published on the electronic Medicines Compendium (eMC), tirzepatide acts as an agonist at both GIP and GLP-1 receptors, with activity at each receptor contributing to its effects on appetite and metabolic regulation.
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Understanding the mechanism is one thing — living with the day-to-day changes it brings is another. GLP Trackr's insights and analytics are designed to help you see how your own body is responding over time, surfacing patterns from your logged data that you might otherwise miss.
Because changes in appetite, energy, and digestion can shift week by week — especially after a dose is adjusted by your prescriber — the app's daily check-in lets you record hunger levels, food noise, mood, and energy in about 30 seconds each morning. Over weeks, these data points build into a personal picture that can be genuinely useful to bring to your next prescriber appointment.
If you experience side effects that seem linked to how the medicine is working — nausea, changes in digestion, or fatigue — the side-effect tracker lets you log these and spot whether they follow a pattern (for example, appearing consistently in the days after each injection). That kind of record is something your healthcare professional can actually use. For a broader view of how the medicine works and what to track, the complete guide to how Mounjaro works covers this in more detail, alongside our look at the mechanism of action of GLP-1 agonists more broadly.
GLP Trackr helps you record what you are experiencing — it is not a substitute for the guidance of your prescriber or doctor. If any symptom feels severe, persistent, or worrying, contact your healthcare professional promptly rather than relying on the app alone.
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Frequently asked questions.
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist. It activates both hormone receptors involved in appetite regulation and blood sugar control, mimicking and amplifying natural gut hormone signals to reduce hunger and slow gastric emptying.
Wegovy (semaglutide) acts on the GLP-1 receptor only, while Mounjaro (tirzepatide) activates both GLP-1 and GIP receptors. Both reduce appetite and slow digestion, but the dual-receptor action is specific to tirzepatide. Which medicine is right for you is a decision for your prescriber.
Many commonly reported side effects — such as nausea, fullness, and changes in digestion — are linked to how GLP-1 and GIP receptor activation slows gastric emptying and affects gut motility. These effects are often most noticeable early on or after a dose change, and frequently ease over time.
Individual response varies. Many people notice reduced appetite relatively early, though the full effect on weight and wellbeing typically develops over weeks and months. Your prescriber is best placed to discuss what to expect based on your personal circumstances.
GLP Trackr lets you log appetite, food noise, energy, mood, and side effects each day, building a personal record of how you are responding. This can be useful to review with your prescriber. The app is available free for 7 days on the App Store and Google Play.