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 Long Does Mounjaro Take To Suppress Appetite?
Appetite suppression with Mounjaro typically begins within the first few days to one week of starting treatment, with effects becoming more noticeable by weeks 2–4 as your body adjusts to the medication. Mounjaro is a dual GIP and GLP-1 receptor agonist, which is why its appetite-suppressing effects may develop differently compared to single-mechanism medications like Wegovy. The speed and strength of appetite suppression varies significantly between individuals and depends on your starting dose, how quickly you titrate up through the doses, and your personal metabolism. Most people notice a meaningful reduction in food cravings and feeling fuller after smaller meals within the first month of consistent use.
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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.
Mounjaro vs Wegovy: Timeline and Mechanism Differences
Mounjaro (tirzepatide) works as a dual GIP and GLP-1 receptor agonist, activating two separate appetite-regulating pathways simultaneously. This dual mechanism means appetite suppression may develop slightly faster and potentially more intensely than single-mechanism medications. In the SURMOUNT-1 clinical trial, participants reported noticeable appetite changes within the first 1–2 weeks, with effects strengthening as doses increased over the 20-week titration phase.
Wegovy (semaglutide) is a GLP-1-only receptor agonist, activating a single hormone pathway. Clinical trials (STEP-1) showed appetite suppression typically begins within days but may take 2–4 weeks to reach optimal levels as patients titrate through doses from 0.25 mg up to 2.4 mg.
- Mounjaro starting dose: 2.5 mg once weekly; titration to 15 mg maximum
- Wegovy starting dose: 0.25 mg once weekly; titration to 2.4 mg maximum
- Key difference: Mounjaro's dual action may produce faster appetite suppression in some individuals, though individual variation is significant
Both medications are prescription-only and require clinical assessment. Your prescriber will discuss which is most suitable based on your personal health profile. Our GLP-1 weight loss calculator can help you understand projected outcomes at different doses.
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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.
Individual Variation: What Influences Your Timeline
How quickly Mounjaro suppresses appetite depends on several personal factors. Your starting dose, rate of dose escalation (minimum 4 weeks per dose), baseline hunger levels, and metabolic factors all influence timeline. Some people notice significant appetite suppression within the first injection, while others experience gradual changes over 3–4 weeks. Body weight, age, and whether you have type 2 diabetes may also play a role—people with diabetes may experience different patterns than those without.
Consistency matters: appetite suppression is most effective when combined with a reduced-calorie diet and increased physical activity. Skipping doses or poor diet adherence can reduce appetite-suppressing effects. Your UK prescriber will monitor your response at follow-up appointments and adjust your approach if needed. Track your appetite changes using our free progress tracker to share observations with your healthcare team.
- 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 many days into Mounjaro before appetite suppression starts?
Most people report appetite changes within 3–7 days of the first injection, though some notice effects within 24 hours. Full appetite suppression typically strengthens over weeks 2–4 as your body adjusts. Individual variation is significant—always discuss your personal timeline with your prescriber.
Is Mounjaro's appetite suppression stronger than Wegovy?
Mounjaro's dual GIP+GLP-1 mechanism may produce appetite suppression that develops faster or feels more intense for some people, but clinical trial data show similar overall weight loss outcomes. Individual results vary considerably—neither is universally "stronger", and suitability depends on your personal health profile and prescriber assessment.
What if Mounjaro doesn't suppress my appetite after 2 weeks?
Some people need 3–4 weeks to experience noticeable appetite suppression, especially at lower doses. If you're on the 2.5 mg starting dose, appetite effects often increase once you escalate to 5 mg or higher. Contact your prescriber if you have concerns—they may adjust your dose timeline or explore alternatives.
Do I need to be on the maximum Mounjaro dose for appetite suppression?
No. Many people experience significant appetite suppression at 5 mg or 7.5 mg doses. The maximum 15 mg dose is not necessary for everyone. Your prescriber will find the dose that balances appetite suppression with tolerability for your individual needs.
How does Mounjaro's appetite suppression compare to dieting alone?
Mounjaro's appetite suppression typically makes it easier to maintain a reduced-calorie diet because you naturally feel less hungry and experience stronger satiety signals. This differs from calorie restriction alone, where hunger often remains challenging. Mounjaro works best alongside dietary changes and physical activity, not as a replacement for them.
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.