How Ozempic and Mounjaro Differ: Active Substances and Mechanisms
The clearest distinction between these two medicines lies in their active substances and how they interact with the body's appetite-regulating systems.
Ozempic (semaglutide)
Ozempic's active substance is semaglutide, a GLP-1 receptor agonist. GLP-1 (glucagon-like peptide-1) is a hormone involved in regulating appetite and blood sugar. By mimicking GLP-1, semaglutide can contribute to increased feelings of fullness and reduced appetite. It is a prescription-only medicine supplied as a pre-filled, once-weekly injectable pen.
It is worth noting that Wegovy also contains semaglutide — the difference between Ozempic and Wegovy is primarily the licensed indication and dose range rather than the active substance. If you are specifically comparing those two, see our page on what separates Ozempic from Mounjaro in more detail, and our related guide on how Mounjaro and Wegovy differ from each other.
Mounjaro (tirzepatide)
Mounjaro's active substance is tirzepatide, a dual GIP and GLP-1 receptor agonist. In addition to the GLP-1 pathway, tirzepatide also acts on GIP (glucose-dependent insulinotropic polypeptide) receptors. This dual mechanism is what distinguishes it from semaglutide-based medicines at a pharmacological level. Like Ozempic, it is prescription-only and administered as a once-weekly injection.
Key factual differences at a glance
- Active substance: Ozempic = semaglutide; Mounjaro = tirzepatide
- Receptor targets: Ozempic = GLP-1 only; Mounjaro = GLP-1 + GIP (dual)
- Frequency: both are once-weekly injections
- Form: both are supplied as pre-filled injectable pens
- Status: both are prescription-only medicines
Both medicines carry additional monitoring requirements and are subject to pharmacovigilance reporting in many countries — if you experience a side effect, you can report it through your national scheme (such as the UK's Yellow Card scheme) and discuss it with your healthcare professional.
For a broader look at how the dose stages of Mounjaro compare, the page on the difference between 2.5 mg and 5 mg Mounjaro may be useful context.
average weekly weight change in the first 16 weeks of Mounjaro & Wegovy use*
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Whichever Medicine You Have Been Prescribed, GLP Trackr Supports Your Journey
GLP Trackr is built for people already prescribed either a semaglutide-based or tirzepatide-based medicine — the app tracks your journey regardless of which pen is in your hand.
Because both medicines follow a once-weekly injection schedule with rotating injection sites, the injection-site tracking and rotation feature is particularly useful: log each site (abdomen, thigh, or upper arm), and the app keeps a history and suggests where to inject next, so rotation becomes effortless rather than something you have to remember manually.
If you notice side effects — which are commonly reported with both medicine classes — the side-effect log lets you record how you feel after each dose and spot patterns over time. That record can be genuinely helpful to bring to your next prescriber appointment, especially when discussing how your body is responding to a particular dose stage.
For a deeper comparison of how these medicines are positioned alongside each other, our hub on Wegovy vs Mounjaro covers the landscape in full.
Any decision about which medicine is appropriate for you — or whether to switch, continue, or adjust — belongs with your prescriber or doctor. GLP Trackr helps you record and understand your experience; it is not a substitute for clinical guidance.
Ready to bring some structure to your weekly routine? GLP Trackr is free to try for 7 days — available now on the App Store and Google Play.
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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.
Injection Tracking
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.
Hydration Reminders
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.
Smart Meal Planning
Personalized meal plans built around your current dose phase and side effects. Every meal is GLP-1 optimized — high in protein, gentle on the stomach, and scaled to your reduced appetite.
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Beautiful, easy-to-read charts show your weight loss trajectory, weekly nutrition trends, medication responses, and wellbeing scores over time — turning raw data into genuine insights.
AI Meal Scanning
Snap a photo of any meal and get a full nutrition breakdown in seconds — calories, protein, carbs, fat, and fibre. No searching. No manual logging. Just point, snap, and track.
Exercise & Steps
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.
Ozempic contains semaglutide, which acts on GLP-1 receptors only. Mounjaro contains tirzepatide, which acts on both GLP-1 and GIP receptors. Both are once-weekly prescription-only injectables, but their active substances and receptor mechanisms are distinct.
Both Ozempic and Wegovy contain the same active substance, semaglutide. They differ primarily in their licensed indication and dose range. Your prescriber or doctor can advise which, if either, has been licensed and prescribed for your specific circumstances.
Neither can be called universally better. These are prescription-only medicines and the right choice for any individual depends on their health history, circumstances, and clinical assessment. That decision belongs with your prescriber or doctor, not a comparison article.
Any change in medication — including switching between medicines — is a clinical decision made by your prescriber or doctor. Do not start, stop, or switch medicines without their guidance.
Yes. GLP Trackr supports people prescribed either medicine. You can log injections, track rotation sites, record side effects, and monitor progress regardless of whether you are taking a semaglutide-based or tirzepatide-based medicine.