What Are These Weight Loss Injections and How Do They Work?
GLP-1 receptor agonists mimic a naturally occurring hormone that signals fullness to the brain and slows gastric emptying — meaning food moves through the stomach more gradually, which many people find reduces overall appetite and what is sometimes called "food noise". Tirzepatide (Mounjaro) also acts on GIP receptors, making it a dual receptor agonist, while semaglutide (Wegovy) acts on GLP-1 receptors alone. Both are supplied as pre-filled injection pens and are typically given once a week.
These are prescription-only medicines. Suitability, dosing, and any adjustments to your treatment are decided entirely by your prescriber or doctor — not by the medicine's general availability. For a broader overview of how these treatments are used, see our guide to weight loss injections.
Common injection sites
Both medicines are given as a subcutaneous injection — into the fatty layer just beneath the skin. The most commonly used sites are:
- Abdomen — the area around the stomach, avoiding the navel
- Front of the thigh
- Upper arm — typically the outer area
Your prescriber or the patient information leaflet that came with your pen will provide guidance on exactly how to use your specific device. If you are unsure about technique, always check with your healthcare professional rather than relying on general information.
Why injection site rotation matters
Using the same spot repeatedly can cause lumps or changes in the skin tissue (lipohypertrophy), which may affect how the medicine is absorbed. Rotating between sites — and varying the exact position within each site — is widely recommended. Keeping a record of where you last injected makes consistent rotation much easier to maintain. For more on this, see our page on managing your weight loss injection and our dedicated guide to Mounjaro injection guidance.
According to NHS guidance, these medicines are prescription-only and should always be used as directed by a clinician.
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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How GLP Trackr Helps You Stay on Top of Your Injections
Staying consistent with a weekly injection schedule — and rotating sites properly — is easier when you have a clear record rather than trying to remember. GLP Trackr's injection-site tracking feature lets you log each site you use, and the app uses that history to suggest your next rotation automatically. Over time, you build a clear picture of your rotation pattern without any mental effort.
Alongside site tracking, the app logs every dose — date, time, and strength — so you always know exactly where you are in your schedule. Gentle dose reminders mean a weekly injection is much less likely to slip your mind during a busy week.
If you want to see how these features fit into the broader picture of tracking your progress, our page on choosing and tracking a weight loss injection covers more ground.
GLP Trackr is a tracking and journaling app — it supports your journey and helps you build a record to discuss with your prescriber, but it is not a substitute for their clinical guidance. If you have any concerns about your injection, a side effect, or your treatment plan, always contact your healthcare professional promptly.
Ready to take the guesswork out of site rotation? GLP Trackr is free to start — download it on the App Store or Google Play and explore it with a 7-day free trial.
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.
The most commonly prescribed injections for weight loss are semaglutide (brand name Wegovy) and tirzepatide (brand name Mounjaro). Both are prescription-only GLP-1 receptor agonists given as once-weekly subcutaneous injections. Your prescriber or doctor will advise which is appropriate for you.
These medicines act on appetite-regulating hormones — primarily GLP-1, and for tirzepatide also GIP — to reduce hunger, increase feelings of fullness, and slow gastric emptying. Many people report reduced appetite and food cravings. Effects vary between individuals and are not guaranteed.
These are prescription-only medicines, and their suitability for any individual is assessed by a prescriber or doctor. They are not suitable for everyone. If you have concerns about safety, side effects, or your personal health history, speak with your healthcare professional — they are best placed to advise you.
Common injection sites are the abdomen, front of the thigh, and outer upper arm. Rotating between sites is recommended to avoid skin changes that can affect absorption. Your patient information leaflet and prescriber provide specific guidance for your pen device.
Yes. GLP Trackr lets you log each injection — site, dose, date, and time — and suggests your next rotation site automatically. It also sends dose reminders so you never miss a weekly injection. The app is free to try for 7 days on the App Store and Google Play.