How Prescription Weight Loss Drugs Work — and What Affects Your Progress
The most widely discussed prescription weight loss medicines right now belong to a class called GLP-1 receptor agonists. Semaglutide (the active substance in Wegovy) acts on GLP-1 pathways involved in appetite regulation. Tirzepatide (the active substance in Mounjaro) acts on both GLP-1 and GIP receptors, making it a dual-action medicine. Both are given as once-weekly subcutaneous injections using pre-filled pens.
How they are thought to work
These medicines act on appetite-regulating pathways in the brain and slow gastric emptying — the rate at which the stomach passes food through. Many people report a significant reduction in appetite and what is sometimes called "food noise" (the persistent mental preoccupation with food). It is worth noting that the stomach-emptying effect often lessens over time as the body adjusts. According to NHS guidance, these medicines are intended to be used alongside a reduced-calorie diet and increased physical activity, under clinical supervision.
Are all weight loss drugs injections?
The highest-profile prescription weight loss medicines currently available are injectable, but not all weight loss medicines come in injection form. Some older prescription options are taken as oral tablets. However, the newer GLP-1 and dual GIP/GLP-1 medicines that have attracted significant attention are all injections at present. Your prescriber or doctor is the right person to discuss which option, if any, is appropriate for you.
What affects how progress unfolds
Results on prescription weight loss medicines vary considerably between individuals. Factors that commonly influence progress include the dose stage you are at (titration typically starts low and increases gradually under prescriber guidance), how consistently you take the medicine, your food and activity habits, sleep, and individual biology. Plateaus are common and do not necessarily mean the medicine has stopped working — they are a normal part of many people's journeys. For a broader look at how these medicines fit into the wider picture, see our overview of weight loss on GLP-1 medicines and our deeper guide to understanding weight loss drugs.
Safety considerations
Prescription weight loss medicines are not suitable for everyone, and suitability is always decided by a prescriber based on your individual health history. Commonly reported side effects include nausea, vomiting, diarrhoea, constipation, and fatigue — particularly in the early weeks or after a dose increase. If you experience side effects that are severe, persistent, or worrying, contact your healthcare professional promptly. Any concerns about adverse effects should also be reported through your national reporting scheme (such as the UK's Yellow Card scheme) as directed by your prescriber.
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Tracking Your Progress on Prescription Weight Loss Drugs
One of the most useful things you can do while on a prescription weight loss medicine is track your progress consistently — not just your weight, but the wider picture of how you are feeling, eating, and living. The scale alone rarely tells the full story.
GLP Trackr's weight and body tracking feature is built for exactly this. You can log your weight regularly, record measurements, and watch your transformation week by week through charts that show genuine trends rather than day-to-day fluctuations. Because weight loss on these medicines is rarely linear, seeing the longer arc of your data is often more meaningful — and more motivating — than any single weigh-in.
Beyond the scale, the insights and analytics tools help you spot patterns in your own data — for example, how your sleep or protein intake correlates with your results, or whether a plateau might be forecast based on your recent trend. You can also use the daily check-in to log mood, energy, food noise, and sleep in under a minute each morning, building a record that reflects how the medicine is affecting your daily life — not just your body weight.
If you want to explore more about what drives results on these medicines, the guide to prescription weight loss medications and your journey is a useful companion read alongside this page.
GLP Trackr is a tracking and journaling app — it is not a substitute for your prescriber's advice, and any decisions about your treatment, dose, or whether to continue should always be made with your healthcare professional. Think of the app as giving you better data to bring to those conversations.
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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.
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
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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.
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Frequently asked questions.
Prescription GLP-1 medicines such as semaglutide and tirzepatide act on appetite-regulating pathways in the brain and slow gastric emptying, which many people experience as reduced hunger and less preoccupation with food. They are taken as once-weekly injections and always prescribed and supervised by a healthcare professional.
The most widely prescribed newer weight loss medicines — including Mounjaro (tirzepatide) and Wegovy (semaglutide) — are given as injections. Some older prescription weight loss options are taken as oral tablets. Your prescriber or doctor is best placed to advise on which form is appropriate for you.
These medicines are prescription-only because suitability depends on individual health history. Commonly reported side effects include nausea, constipation, and fatigue. They are not suitable for everyone. Always follow your prescriber's guidance, and contact a healthcare professional promptly if you experience severe or persistent side effects.
Plateaus are common on GLP-1 medicines and do not necessarily mean the medicine has stopped working. Progress is rarely linear and is influenced by dose stage, diet, activity, sleep, and individual biology. Tracking your full data over time — not just the scale — can help you and your prescriber understand what is happening.
GLP Trackr lets you log weight, measurements, daily mood, energy, and food intake in one place. Charts and weekly insights show your trend over time, which is more informative than individual weigh-ins. The app is a tracking companion — all clinical decisions remain with your prescriber or doctor.