Mounjaro and Wegovy: What the Medicines Actually Are
Both Mounjaro and Wegovy are prescription-only injectable medicines taken once a week using pre-filled pens. Understanding what they are — and what distinguishes them — is useful context for anyone already on one of them.
Mounjaro (tirzepatide)
Mounjaro's active substance is tirzepatide, which acts on two appetite-related receptors: GIP and GLP-1. It is typically started at a low dose and adjusted over time by the prescriber. It is supplied as a pre-filled KwikPen device and is subject to additional monitoring — any side effects should be reported to your healthcare professional and, where applicable, to your national reporting scheme (such as the UK's Yellow Card scheme).
Wegovy (semaglutide)
Wegovy's active substance is semaglutide, a GLP-1 receptor agonist. Like Mounjaro, it is a once-weekly injectable taken via a pre-filled pen, started at a low dose and titrated under prescriber guidance. It is also subject to additional monitoring and the same reporting principles apply.
How they work
Both medicines act on appetite-regulating pathways in the brain, and many people experience a reduced sense of hunger and decreased "food noise." Mounjaro additionally acts on GIP receptors, which is a pharmacological difference — but whether that difference matters for you specifically is a clinical question for your prescriber, not something a comparison article can answer.
For a broader look at how these options sit within the wider landscape, see our guide to weight loss injections or read more about injectable weight loss medicines generally.
What neither medicine is
- Neither is insulin
- Neither is suitable for everyone — suitability is decided by a prescriber
- Neither is a substitute for clinical supervision, diet, and activity
- Neither is available without a prescription
If you are weighing up the options with your prescriber, our page on choosing a weight loss injection covers the key factual differences in more detail, and you can also explore what to consider when selecting an injection for weight loss.
average weekly weight change in the first 16 weeks of Mounjaro & Wegovy use*
Tracking the right four numbers — weight, waist, protein and dose — turns a noisy chart into a clear story. That's the loop GLP-1 users keep coming back for.
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Tracking Your Injectable Medicine with GLP Trackr
Whichever injectable medicine you have been prescribed, staying consistent with your weekly injection schedule matters — and that is where GLP Trackr is built to help.
The app's injection-site tracking and rotation feature is particularly useful for people using pre-filled pens week after week. You log each injection — including the site you used (abdomen, thigh, or upper arm) — and the app keeps a running history so it can suggest your next rotation site automatically. Rotating sites is important for skin health, and having a record removes the guesswork.
Alongside site tracking, dose logging means every injection is timestamped with the dose strength and date, giving you a clear record to refer back to or share at your next prescriber appointment. If you ever miss a dose and need to discuss it with your healthcare professional, that logged history is right there — the app does not advise on what to do about a missed dose, but it helps you have an informed conversation.
GLP Trackr also lets you log side effects — nausea, fatigue, injection-site reactions — so you can spot patterns over time and bring a meaningful summary to your prescriber rather than relying on memory.
Remember: any decision about your dose, injection schedule, or which medicine is right for you belongs with your prescriber or doctor. GLP Trackr is a tracking tool that helps you stay organised and informed — it is not a substitute for their guidance.
Ready to take the guesswork out of your weekly injection routine? GLP Trackr is free to try for 7 days — available on the App Store and Google Play. Log your first injection today and let the app handle your rotation history from there.
What does glptrackr include?
10+ powerful features. One app. Built specifically for Mounjaro and Wegovy users.
Everything your GLP-1 journey needs. Free to try for 7 days.
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.
Recipe Library
Browse 50+ high-protein, GLP-1-friendly recipes filtered by meal type, prep time, and dietary needs. Every recipe includes full nutrition info, step-by-step instructions, and tips for eating with side effects.
Progress Analytics
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.
Community Support
Connect with thousands of others navigating the same medication journey. Share milestones, ask questions, find accountability partners, and get support from people who truly understand.
Never Forget a Dose Again.
Log your Mounjaro or Wegovy injection in seconds. Track your pen, your dose level, and your injection site — so you always know exactly where you are in your treatment.
Watch Your Body Transform, Week by Week.
Log your weight, measurements, and how you're feeling after each dose. GLPTrackr turns your data into clear, motivating charts that show you how far you've really come.
You're Not on This Journey Alone.
Connect with thousands of real GLP-1 users sharing their wins, side effect tips, and meal ideas. Get the support of people who truly get it — because they're living it too.
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The Most Advanced GLP-1 Brain Ever Built.
The first AI built exclusively for GLP-1 weight loss. Every insight, every meal plan, every prediction trained on one thing only: helping you get the most out of your medication.
Knows Your Cycle
GLPIQ tracks where you are in your injection cycle and adjusts everything around it: lighter meals on nausea days, higher protein when appetite returns, and smarter targets as your medication level shifts.
Predicts Before You Feel It
GLPIQ learns your personal side effect patterns over time. After a few cycles, it starts warning you the morning before a rough day — and adjusts your meal plan automatically.
Finds Your Golden Dose
GLPIQ analyses every dose you've been on: weight loss rate, side effects, food noise, mood, protein adherence and tells you which dose gave you the best results. No other app does this.
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Frequently asked questions.
There is no universally "best" injectable weight loss medicine. Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are prescription-only options used for weight management. The right choice depends on your individual health profile and is a decision for your prescriber or doctor, not a general comparison.
Mounjaro contains tirzepatide, which acts on both GIP and GLP-1 receptors. Wegovy contains semaglutide, a GLP-1 receptor agonist. Both are once-weekly injectables prescribed for weight management. A prescriber can advise which, if either, is appropriate for an individual's circumstances.
Yes. Both Mounjaro and Wegovy are prescription-only medicines. They are not available without a valid prescription from a qualified prescriber. Suitability, dosing, and access are all determined through a clinical assessment with a healthcare professional.
GLP Trackr lets you log each injection — recording the dose, date, and injection site. It tracks your rotation history and can suggest the next site, so you always know where to inject next. It also sends dose reminders so a weekly shot is never accidentally missed.
Decisions about a missed dose belong with your prescriber or doctor — do not adjust your schedule without their guidance. GLP Trackr can log a missed dose so you have an accurate record to discuss at your next appointment. Refer to the patient information leaflet supplied with your medicine for general missed-dose guidance.