The UK's most complete GLP-1 guide
Every Question Answered. Every Side Effect Explained.
- How GLP-1 medications work
- Mounjaro vs Wegovy compared
- Injection instructions
- Side effects & solutions
- What to eat on treatment
- FAQs answered
Free tracker included with every download this week
How Quickly Does Mounjaro Suppress Appetite?
Mounjaro (tirzepatide) begins working on appetite suppression within the first few days of your first injection, though most people notice the most significant effects by week 2 to week 4. As a dual GIP and GLP-1 receptor agonist available on NHS specialist services and privately in the UK, Mounjaro works by signalling to your brain that you're fuller sooner and reducing food cravings. However, the speed and extent of appetite suppression varies between individuals and often increases as your dose is gradually escalated according to your prescriber's guidance.
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Enter your height and weight below. Supports both imperial (stone & lbs) and metric (kg). Results include NHS category, healthy weight range, and ethnicity adjustments.
What Is BMI and Why Does It Matter?
Body Mass Index (BMI) is the most widely used screening tool for assessing whether your weight falls within a healthy range. Used by the NHS, GPs, and weight management services across the UK, BMI provides a quick snapshot of your weight relative to your height. The formula is simple: your weight in kilograms divided by your height in metres squared (kg/m²).
While BMI isn't a perfect measure — it doesn't account for muscle mass, bone density, or fat distribution — it remains the standard first step in identifying potential weight-related health risks including type 2 diabetes, cardiovascular disease, high blood pressure, and certain cancers.
The NHS also recommends adjusted thresholds for people of South Asian, Chinese, or Black African heritage — a BMI of 23 or above is classified as overweight, and 27.5 as obese. Our calculator includes this adjustment as a one-click toggle.
Timeline for Appetite Suppression: What Happens Week by Week
Week 1–2 (Starting dose 2.5 mg): Some people report reduced appetite within 24–48 hours, though effects are often subtle at this starting dose. You may notice you feel satisfied with smaller meal portions or have fewer cravings for snacks between meals.
Week 3–4: Appetite suppression typically becomes more noticeable. Many users report feeling fuller sooner and losing interest in foods they previously craved. The "fullness signal" becomes clearer.
Week 5 onwards (after dose increases): As your dose escalates through the titration schedule (5 mg, 7.5 mg, 10 mg, 12.5 mg, 15 mg), appetite suppression usually intensifies. Peak effects often occur 4–6 weeks after reaching your maintenance dose.
Important: Individual timing varies significantly. Some people feel dramatic appetite reduction in week 1; others take 6–8 weeks to notice substantial changes. Your prescriber will monitor how you respond at each dose level.
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How It Works
Three simple steps to understand your weight and take action.
Enter your height and weight in our free calculator. Get your BMI, NHS category, healthy weight range, and ethnicity-adjusted thresholds instantly.
If your BMI suggests you're overweight or obese, explore our GLP-1 calculators to project potential weight loss on Mounjaro or Wegovy.
Use our progress tracker to log your weight weekly, visualise your journey with charts, and stay motivated — all stored privately in your browser.
Free Weight Loss Tools & Guides
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
How Mounjaro's Appetite Suppression Mechanism Works
Mounjaro's dual action on GIP and GLP-1 receptors creates appetite suppression through multiple pathways. The medication signals to your hypothalamus (the brain's hunger centre) that you've eaten enough, slows stomach emptying so food stays longer, and reduces the hormone signals that trigger cravings. This dual mechanism means appetite suppression can feel different from single GLP-1 medications like Wegovy — many users describe it as a gentle, sustained reduction in interest in food rather than a sudden loss of appetite. The effect builds gradually and typically feels most natural by week 4–6 as your body adjusts to the medication. Using our free GLP-1 weight loss calculator can help you understand projected outcomes based on similar trial data.
- Dual GIP/GLP-1 receptor agonist
- Up to 22.5% body weight loss (SURMOUNT-1)
- Weekly injection, dose escalation over 20+ weeks
- Available via private prescription in the UK
- Doses: 2.5mg → 5mg → 7.5mg → 10mg → 12.5mg → 15mg
- GLP-1 receptor agonist
- Up to 15–17% body weight loss (STEP trials)
- Weekly injection, 5-step dose escalation
- NHS & private prescription available
- Doses: 0.25mg → 0.5mg → 1mg → 1.7mg → 2.4mg
Mounjaro vs Wegovy: Head-to-Head
A side-by-side comparison of the two most popular GLP-1 weight loss medications available in the UK.
| Feature | Mounjaro | Wegovy |
|---|---|---|
| Drug class | Dual GIP/GLP-1 agonist | GLP-1 agonist |
| Active ingredient | Tirzepatide | Semaglutide |
| Avg. weight loss | 15–22.5% | 12–17% |
| Key trial | SURMOUNT-1 (2022) | STEP 1 (2021) |
| Max dose | 15 mg weekly | 2.4 mg weekly |
| Escalation period | 20–32 weeks | 16–20 weeks |
| Administration | Weekly injection (pen) | Weekly injection (pen) |
| NHS availability | Private prescription only | NHS & private |
| Approx. private cost | £150–£250/month | £150–£300/month |
| Common side effects | Nausea, diarrhoea, constipation | Nausea, vomiting, diarrhoea |
Data sourced from SURMOUNT-1 and STEP 1 clinical trials. Costs are approximate and vary by provider. Always consult a prescriber.
Am I Eligible for Weight Loss Medication?
In the UK, eligibility for GLP-1 weight loss medications like Mounjaro and Wegovy is based on your BMI and overall health profile.
- BMI of 30 or above (obese)
- Age 18 or over
- No contraindicated conditions
- Committed to lifestyle changes
- BMI of 27 or above
- Plus type 2 diabetes
- Or high blood pressure
- Or obstructive sleep apnoea
Use our BMI calculator to check whether your BMI falls within the eligible range.
How We Built These Tools
Every calculator and guide on myweightcheck is built with accuracy and transparency in mind. Our BMI calculator uses the standard WHO formula with NHS-aligned category thresholds. Our GLP-1 projections are modelled on published clinical trial data from SURMOUNT and STEP studies.
All data stays on your device. We don't require sign-ups, and we don't store your health information on any server. Your progress tracker saves data locally in your browser using localStorage, so only you can see it.
We're based in the UK and our tools are designed specifically for UK users — supporting stone & lbs by default, referencing NHS guidelines, using NICE-approved medication data, and linking to GPhC-registered pharmacies.
Frequently Asked Questions
Common questions about BMI, weight loss medications, and our free UK tools.
How long does it take for Mounjaro to suppress appetite?
Most people notice appetite suppression beginning within a few days to a week, with more noticeable effects by week 2–4. At the starting dose of 2.5 mg, changes may be subtle. Appetite suppression typically intensifies as your dose increases during the titration schedule. Individual timelines vary — some people feel significant changes in week 1, while others take 6–8 weeks.
Why does appetite suppression take time with Mounjaro?
Mounjaro uses a gradual dose escalation schedule, starting at 2.5 mg and increasing every 4 weeks. Your body needs time to adjust to each dose level, and the appetite-suppressing effects build with each increase. This slower approach reduces side effects and helps your body adapt safely to the medication.
Is appetite suppression the same at every Mounjaro dose?
No. Appetite suppression typically increases as your dose escalates. At 2.5 mg, effects are often subtle. By 5 mg and above, appetite suppression becomes more pronounced. By 10–15 mg (maintenance doses), most people report significant reduction in hunger and cravings compared to lower doses.
What if I don't feel appetite suppression after 2 weeks on Mounjaro?
This is not unusual at the starting dose of 2.5 mg. Many people don't notice substantial appetite changes until week 3–4 or after their first dose increase to 5 mg. If you've reached 5 mg and still feel no appetite suppression after 4 weeks, discuss this with your prescriber — dose adjustment or alternative assessment may be needed.
Does Mounjaro's appetite suppression feel different from Wegovy?
Yes, often. Mounjaro's dual GIP and GLP-1 action can produce a gentler, more sustained appetite reduction compared to Wegovy's single GLP-1 mechanism. Some users report less nausea with Mounjaro's appetite suppression. However, individual experiences vary — what matters is your own response and how your prescriber guides your treatment plan.
Ready to take control of your weight loss journey?
Start with a free BMI check, explore your GLP-1 options, or begin tracking your progress today. No sign-up. No cost. Just results.