How Mounjaro and Wegovy Differ: Active Substances and Mechanisms
At their core, Mounjaro (tirzepatide) and Wegovy (semaglutide) belong to the same broad class of injectable weight-management medicines but have different mechanisms of action.
Active substances
- Mounjaro — active substance tirzepatide, a dual GIP and GLP-1 receptor agonist. It acts on both glucose-dependent insulinotropic polypeptide (GIP) receptors and glucagon-like peptide-1 (GLP-1) receptors.
- Wegovy — active substance semaglutide, a GLP-1 receptor agonist. It acts on GLP-1 receptors only.
Commonly reported effects
Both medicines are associated with a reduced sense of appetite and increased feelings of fullness, effects that many people describe as reduced "food noise". Slower gastric emptying is also commonly reported with both, though the degree and duration of this effect can vary from person to person.
Dose strengths
The two medicines use different dose scales and should never be compared milligram for milligram. Mounjaro is commonly titrated through strengths such as 2.5 mg, 5 mg, 7.5 mg, 10 mg, 12.5 mg, and 15 mg. Wegovy is typically titrated through 0.25 mg, 0.5 mg, 1 mg, 1.7 mg, and 2.4 mg. In both cases, the starting dose and any increases are decided by the prescriber, not the patient. For a closer look at what the titration steps mean in practice, see our guide to the difference between Mounjaro dose strengths.
Presentation
Both are supplied as pre-filled injectable pens for once-weekly subcutaneous injection. The pen devices and administration steps differ between the two medicines — always follow the instructions in the patient information leaflet supplied with your specific pen, or ask your prescriber or pharmacist.
Regulatory status and monitoring
Both medicines carry a black triangle (▼) designation in the UK, meaning they are subject to additional monitoring. Any suspected side effects should be reported to your national pharmacovigilance scheme (such as the UK Yellow Card scheme) and to your healthcare professional. You can find factual prescribing information on the electronic Medicines Compendium (eMC).
If you are also researching how semaglutide compares to another injectable medicine, our page on the difference between Mounjaro and Ozempic covers tirzepatide versus the lower-dose semaglutide product used in type 2 diabetes management.
average weekly weight change in the first 16 weeks of Mounjaro & Wegovy use*
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Whichever Medicine You Take, GLP Trackr Tracks Your Journey
GLP Trackr is built for people already prescribed either Mounjaro or Wegovy — and it supports both equally. The app does not sell, supply, or recommend any medicine; it helps you stay consistent and understand your own progress once treatment is underway.
See your full journey in one place
The most relevant feature for anyone comparing or switching between medicines is the weight and body tracking tool. Log your weight, measurements, and daily check-in data (mood, energy, sleep, food noise), and the app builds a clear week-by-week picture of how your journey is progressing — useful context to bring to your prescriber appointments, whichever medicine you are on.
Log every dose and never lose your place
Because both Mounjaro and Wegovy are titrated over time, keeping an accurate record of which dose you have taken and when is genuinely useful. GLP Trackr lets you log each injection — dose strength, date, time, and site — so your history is always to hand. Dose reminders help make sure a weekly injection is never accidentally missed.
For a deeper comparison of the two medicines and the research behind them, visit our main Wegovy vs Mounjaro guide. You may also find it helpful to read the more detailed breakdown at what's the difference between Mounjaro and Wegovy.
A note on cost: Many people searching for the price difference between Mounjaro and Wegovy are already on one of these medicines and thinking about value for money. GLP Trackr does not display or compare medicine prices — those vary by country, prescriber, and pharmacy. For accurate pricing, speak with a registered pharmacy or your prescriber directly.
Any decision about which medicine to take, or whether to switch, belongs with your prescriber or doctor — they have the full picture of your health history. GLP Trackr helps you record and understand your journey; it is not a substitute for professional clinical advice.
Ready to bring your tracking together in one place? GLP Trackr is available free on the App Store and Google Play, with a 7-day trial so you can explore everything before committing — download it today and start building your progress record.
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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.
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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.
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Frequently asked questions.
Mounjaro contains tirzepatide, which acts on both GLP-1 and GIP receptors. Wegovy contains semaglutide, which acts on GLP-1 receptors only. Both are prescription-only, once-weekly injections for weight management, but they are different medicines with different active substances.
That is a decision for your prescriber or doctor, based on your individual health history, circumstances, and clinical needs. Neither medicine can be described as universally better; suitability varies from person to person and is not something a tracking app or general content can determine.
Prices vary by country, prescriber, and pharmacy and can change over time. GLP Trackr does not display or compare medicine prices. For accurate, up-to-date cost information, speak with a registered pharmacy or your prescriber directly.
Any decision to switch between medicines must be made with your prescriber or doctor. They will consider your medical history, current dose, and individual circumstances. Never stop, start, or swap a prescription medicine without clinical guidance.
Yes. GLP Trackr is built for people already prescribed either Mounjaro or Wegovy. You can log injections, track weight and side effects, and monitor progress regardless of which medicine your prescriber has prescribed.