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?
Mounjaro (tirzepatide) can start affecting appetite within days of your first injection, though most people notice stronger appetite suppression between weeks 2 and 4. The medication works by activating two natural hormone pathways—GIP and GLP-1—that regulate hunger signals and feelings of fullness. However, individual timelines vary significantly. Some people report reduced cravings within the first week, while others experience more gradual changes over several weeks. Your GP or prescriber can explain what to expect based on your individual response.
10,000+ calculations today · NHS-aligned thresholds · 100% free
Calculate Your BMI Instantly
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.
When Does Appetite Suppression Start?
Most people taking Mounjaro begin noticing reduced appetite within the first 2–4 weeks of starting treatment at the 2.5 mg starting dose. However, the timeline can vary:
- Days 1–7: Some users report early appetite reduction or slight nausea, though this is not assured
- Weeks 2–4: Appetite suppression typically becomes more noticeable; most people feel fuller after smaller meals
- Weeks 4–8: As your dose increases (usually to 5 mg), appetite suppression often intensifies
- Weeks 8–12: Further dose escalation may enhance the effect further
The dual GIP and GLP-1 mechanism of tirzepatide is what makes it distinct from single-action GLP-1 medications like Wegovy (semaglutide). This dual action may contribute to faster or more pronounced appetite reduction in some individuals, though results vary. With the Mounjaro KwikPen device, you'll inject once weekly, and cumulative effects build over successive doses.
Clinically BackedWeight Loss
No appointments. No waiting rooms. Just care — from a UK-regulated online pharmacy.
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.
What Affects How Quickly Appetite Suppression Works?
Several factors influence how quickly you experience appetite suppression on Mounjaro:
- Your individual metabolism: Genetics and body chemistry affect medication response timing
- Dose level: Starting dose (2.5 mg) produces milder effects; appetite suppression typically increases as you progress through dose titration toward higher maintenance doses
- Stomach emptying rate: Mounjaro slows how quickly food leaves your stomach—this effect is strongest early on and may reduce over time
- Diet and lifestyle: Eating smaller, protein-rich meals and staying hydrated can amplify the appetite-suppressing effect
- Other medications: Certain drugs may interact and affect how quickly Mounjaro works
Your prescriber will monitor your response and adjust your Mounjaro UK prescription and dosing schedule accordingly. Use our free GLP-1 weight loss calculator to explore projected timelines based on different doses.
- 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 does Mounjaro suppress appetite compared to Wegovy?
Both are prescription-only injectables, but Mounjaro (tirzepatide) uses a dual GIP + GLP-1 mechanism, while Wegovy (semaglutide) acts on GLP-1 alone. Clinical trials suggest Mounjaro may produce appetite suppression more rapidly in some people, though individual variation is significant. Your prescriber can advise which is more appropriate for you.
Will appetite suppression continue if I stay on the same Mounjaro dose?
Appetite suppression tends to remain stable once you reach your maintenance dose, though some people report the effect is strongest in the first 12–16 weeks. The stomach-emptying effect (which contributes to early satiety) may gradually reduce over time. Your GP can discuss whether dose adjustments are needed.
What if I don't notice appetite suppression after 4 weeks?
Not everyone experiences noticeable appetite suppression immediately. Differences in metabolism, dose level, and individual physiology mean some people need 6–8 weeks or a higher dose before effects become apparent. Contact your prescriber if you have concerns—they may recommend dose escalation or review your overall treatment plan.
Can I speed up appetite suppression on Mounjaro?
No—skipping ahead in your dose titration schedule is not recommended and can increase side effects. Following the standard 4-week intervals between dose increases (via the KwikPen) is safest. Combining Mounjaro with a structured reduced-calorie diet and increased physical activity supports optimal results.
Does appetite suppression mean I won't feel hungry at all?
Mounjaro typically reduces excessive hunger and cravings, not eliminate hunger entirely. You should still eat regular, nutritious meals—hunger suppression is meant to support portion control and reduced snacking, not complete appetite elimination. This is why lifestyle changes alongside medication are important for sustainable weight management.
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.