Mounjaro and Wegovy: The Two Main Weight Loss Injections
Mounjaro and Wegovy are the brand names most commonly associated with prescription weight loss injections. They belong to a class of medicines called GLP-1 receptor agonists, which act on pathways in the brain and gut that regulate appetite and feelings of fullness.
Mounjaro (tirzepatide)
Mounjaro's active substance is tirzepatide. It is a dual GIP and GLP-1 receptor agonist, meaning it acts on two appetite-related pathways. It is supplied as a pre-filled pen and is injected once a week. Dose strengths are typically started low and adjusted over time by a prescriber — common strengths include 2.5 mg, 5 mg, 7.5 mg, 10 mg, 12.5 mg, and 15 mg. Mounjaro carries a black triangle (▼) in the UK, meaning side effects should be reported to your national reporting scheme (such as the UK's Yellow Card scheme) and to a healthcare professional.
Wegovy (semaglutide)
Wegovy's active substance is semaglutide. It is a GLP-1 receptor agonist, also injected once a week via a pre-filled pen. Dose strengths range from 0.25 mg up to 2.4 mg and are titrated upward under prescriber guidance. Like Mounjaro, Wegovy also carries the ▼ symbol and side effects should be reported accordingly.
What they have in common
- Both are prescription-only medicines — suitability is decided by a prescriber, not the individual
- Both are administered by subcutaneous injection, typically into the abdomen, thigh, or upper arm
- Both are commonly associated with effects such as reduced appetite, increased feelings of fullness, and slower stomach emptying
- Neither is insulin, and neither is a substitute for dietary changes and clinical supervision
For a broader look at how these medicines are used, see our guide to weight loss injections. You may also find it useful to read about how the weight loss injection works in more detail.
average weekly weight change in the first 16 weeks of Mounjaro & Wegovy use*
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Tracking Your Injection Journey with GLP Trackr
Once you have been prescribed a weight loss injection, one of the most practical things you can do is keep a consistent record of every dose — and that starts with knowing exactly where and when you last injected.
Injection-site tracking and rotation is the feature at the heart of GLP Trackr for people who are already injecting. Each time you administer your dose, you log the site (abdomen, thigh, or upper arm) in the app. GLP Trackr keeps a rotation history and suggests your next site automatically, so you never have to remember which spot you used last week. Rotating sites matters because using the same location repeatedly can affect how the medicine is absorbed.
Alongside site tracking, the app also logs your dose strength, date, and time for every injection, and sends gentle dose reminders so a weekly shot does not slip your mind. Everything is stored in one place, making it straightforward to bring a clear summary to your next prescriber appointment.
If you have questions about the costs involved with weight loss injections or are looking for general information on how these medicines are accessed, those pages can help point you in the right direction.
Any questions about which injection is right for you, your current dose, or how to administer it correctly should always be directed to your prescriber or doctor — they know your full medical history and are best placed to guide you.
Ready to keep track of every dose and injection site in one place? GLP Trackr is free to try for 7 days on the App Store and Google Play — download it and let the app handle the rotation reminders from your very first shot.
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.
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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.
The two main prescription weight loss injections are Mounjaro (tirzepatide) and Wegovy (semaglutide). Both are once-weekly injectable medicines available only on prescription. Your prescriber or doctor will determine which, if either, is appropriate for you.
Mounjaro contains tirzepatide, a dual GIP and GLP-1 receptor agonist, while Wegovy contains semaglutide, a GLP-1 receptor agonist. Both are once-weekly injections prescribed for weight management. Which is suitable for you is a decision for your prescriber, not one to make independently.
These injections are typically administered subcutaneously into the abdomen, thigh, or upper arm. Rotating sites between injections is generally recommended. Your prescriber or the patient information leaflet supplied with your pen will give you specific guidance on technique.
GLP Trackr lets you log each injection's site, dose strength, date, and time. It tracks your rotation history and suggests your next site automatically, and sends dose reminders so you never miss a weekly shot. It is a tracking tool, not a medical service.
Suitability is assessed by a prescriber based on your individual health history — these medicines are not appropriate for everyone. If you have concerns about side effects or safety, contact your prescriber or doctor promptly rather than making any changes on your own.