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
Does Mounjaro Suppress Appetite Immediately?
Mounjaro (tirzepatide) does not typically suppress appetite immediately. Most people experience appetite changes gradually over the first few weeks of treatment, as the medication builds up in their system. Understanding the timeline helps set realistic expectations for this prescription-only weight management injection. The effects become more noticeable as your dose increases and your body adjusts to the medication. Our GLP-1 weight loss calculator can help you explore what appetite suppression at different doses might mean for potential weight loss outcomes.
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.
How Long Does Appetite Suppression Take?
Mounjaro works by acting as a dual GIP and GLP-1 receptor agonist — activating two natural hormone pathways involved in appetite regulation and feeling fuller after meals. However, this process is gradual, not immediate. Most people starting at the 2.5 mg dose (the starting dose) notice subtle appetite changes within 3–5 days, but these are usually mild. More noticeable appetite suppression typically develops over 1–2 weeks as your body adjusts to the medication and as your dose increases. By weeks 5–8, when you progress to higher doses (5 mg and beyond), appetite-suppressing effects usually become more pronounced. Individual experiences vary significantly — some people report feeling less hungry within days, whilst others take 2–3 weeks to notice meaningful changes. Clinical trials showed that the strongest appetite suppression and weight loss benefits occur at higher maintenance doses (10 mg and 15 mg), not at the starting dose.
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 You Feel Appetite Suppression?
Several factors influence how quickly you experience appetite suppression with Mounjaro. Your individual metabolism and GLP-1 sensitivity play a major role — some people's bodies respond faster to tirzepatide than others. Dose timing matters too: you're on a gradual escalation schedule (2.5 mg, then 5 mg, then 7.5 mg, and potentially higher), so appetite effects typically build week by week. Your eating habits and meal timing also affect how you perceive appetite changes — if you eat regularly, you may notice reduced hunger sooner than if you skip meals. Medical conditions like gastroparesis or digestion issues can slow the onset of appetite suppression. For personalised guidance on what to expect, use our BMI calculator and discuss the timeline with your prescriber during your clinical assessment.
- 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.
Will Mounjaro suppress my appetite on the first injection?
Most people do not experience immediate appetite suppression from the first 2.5 mg dose. The starting dose is deliberately low to allow your body to adjust. Mild changes may occur within days, but noticeable appetite suppression usually develops over 1–2 weeks as your dose increases and your system adapts to tirzepatide.
What does appetite suppression feel like on Mounjaro?
People describe appetite suppression differently. Common experiences include feeling full sooner when eating, reduced cravings for specific foods, less frequent hunger signals, and needing smaller portion sizes. Some describe it as a gentle "fullness" rather than forced appetite loss. Effects vary between individuals.
Is there a difference between Mounjaro and Wegovy for appetite suppression speed?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist, whilst Wegovy (semaglutide) is a GLP-1-only agonist. Some people report that Mounjaro's dual mechanism may produce faster appetite suppression, but clinical trials show both medications have gradual onset. Individual variation is significant — timing depends more on your personal response than the medication type.
What if I don't feel appetite suppression after 2 weeks on Mounjaro?
If you're still on the 2.5 mg starting dose after 2 weeks, it's normal — this dose is intentionally mild. Appetite effects typically increase as your dose escalates to 5 mg and higher (weeks 5–8 onwards). If you're on a higher dose and feel no appetite changes, discuss this with your prescriber — they may adjust your dose or assess whether the medication is right for you.
Can appetite suppression wear off over time on Mounjaro?
Some people report that the appetite-suppressing effects of gastric slowdown (feeling very full after small meals) may reduce slightly after several months, as the body adapts. However, the appetite-regulating effects through GIP and GLP-1 pathways typically continue. Your prescriber can discuss long-term effectiveness during your regular check-ins.
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.