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
When Does Appetite Suppression Start With Mounjaro?
Appetite suppression with Mounjaro typically begins within the first week of your first injection, though the timing and intensity vary between individuals. Most people notice reduced hunger and earlier fullness within 2–4 days of starting the 2.5 mg starting dose. The effect increases gradually as your body adjusts to the medication and as your dose increases over the following weeks. Understanding this timeline helps you know what to expect and when to discuss progress with your prescriber.
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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.
Appetite Suppression Timeline and Dose Titration
Mounjaro works through dual GIP and GLP-1 receptor activation, which signals fullness and reduces hunger. The appetite suppression timeline depends on your dose titration schedule:
- Week 1–4 (2.5 mg): Most people notice reduced appetite within 2–4 days; effects are mild at this starting dose
- Week 5–8 (5 mg): Appetite suppression becomes more pronounced as your body adjusts; many experience stronger fullness signals
- Week 9–12 (7.5 mg): Further increases in satiety and reduced food cravings as the dose escalates
- Week 13+ (10 mg, 12.5 mg, 15 mg): Maximum appetite suppression typically achieved by weeks 13–20 depending on your final maintenance dose
Individual variation is significant — some notice effects within hours, others take 1–2 weeks. Nausea, which is common early on, can also influence appetite.
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.
NHS Access vs Private Routes and Cost Context
In the UK, Mounjaro is available through two routes: NHS specialist tier 3/4 weight management services (via GP referral, often with long waiting lists) or private online prescription services (faster access following an online clinical assessment). Private Mounjaro costs vary by dose and provider, typically ranging from £130–£250+ per month depending on your dose strength and supplier. Each Mounjaro KwikPen contains four weekly doses and is used for one month. NHS access is free but availability is limited and varies significantly by region (ICB). Private prescribing offers quicker access without NHS referral but requires self-funding.
- 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 quickly does appetite suppression actually start after my first Mounjaro injection?
Most people notice reduced appetite and earlier fullness within 2–4 days of their first 2.5 mg injection. Some notice changes within 24 hours; others take 1–2 weeks. Initial effects at the starting dose are typically mild. The suppression increases as your dose escalates over subsequent weeks.
Will appetite suppression be stronger if I access Mounjaro privately versus waiting for NHS referral?
No — the medication itself is identical whether accessed privately or through the NHS. Timing differs: private routes offer faster access (often within 1–2 weeks), while NHS waiting lists can be months or years in many regions. The appetite suppression timeline and intensity depend on your individual response, not your access route.
What's the difference between Mounjaro and Wegovy in terms of appetite suppression timing?
Mounjaro (tirzepatide) is a dual GIP+GLP-1 agonist, while Wegovy (semaglutide) is GLP-1 only. Both start working within days, but Mounjaro's dual mechanism may produce stronger appetite suppression. Mounjaro uses once-weekly doses from 2.5 mg; Wegovy starts at 0.25 mg daily. Timing is broadly similar, but individual response varies.
What happens if appetite suppression stops or reduces after a few weeks on Mounjaro?
Some tolerance to appetite suppression can develop over weeks or months — this is normal. Increasing your dose (if you haven't reached the maximum 15 mg) often restores the effect. If you reach your maintenance dose and appetite suppression plateaus, discuss this with your prescriber. Maintaining lifestyle changes remains important throughout treatment.
Can I use the GLP-1 weight loss calculator to estimate my weight loss with Mounjaro?
Yes — MyWeightCheck's free GLP-1 weight loss calculator helps you estimate potential weight loss based on clinical trial data at different Mounjaro doses. Enter your current weight and target dose to see projected outcomes. Remember that appetite suppression is one factor affecting weight loss; dietary changes and physical activity are equally important for results.
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.