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
Why Has Your Mounjaro Weight Loss Stopped?
It's common for weight loss to slow or plateau after several weeks on Mounjaro, even though you're taking your weekly weight loss injection regularly. This doesn't mean the medication has stopped working entirely — your body may have adapted to the current dose, or you've reached a natural point where weight loss slows. Understanding why this happens and what options are available can help you decide next steps with your prescriber. Your GP or specialist can assess whether a dose adjustment or lifestyle review is needed.
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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.
Why Weight Loss Plateaus on Mounjaro
Weight loss plateaus are a normal part of any weight management journey. When taking Mounjaro (tirzepatide), a plateau typically occurs because your body has adapted to the current dose — your appetite-suppressing response may have reduced slightly, or you've reached a stable point where further loss requires additional changes. The dual GIP and GLP-1 receptor agonist mechanism that initially supported weight loss can become less pronounced as your body adjusts.
Other common reasons for stalled weight loss include:
- Current dose may be below your therapeutic threshold — dose titration (gradual increases from 2.5 mg up to 15 mg) continues for weeks, so you may not yet be at an optimal dose
- Calorie intake has increased slightly without noticing — portion sizes can drift upwards over time
- Physical activity has decreased compared to when you started treatment
- Hormonal factors or underlying health conditions may affect metabolism
- You've lost a significant amount of weight already — the body naturally resists further loss as it adjusts to a new set point
Clinical trials showed that participants on Mounjaro continued losing weight throughout the treatment period, though the rate typically slows after the initial weeks. Individual results vary considerably.
Clinically BackedWeight Loss
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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.
What You Can Do About a Weight Loss Plateau
If your weight has plateaued, discuss this with your prescriber at your next review — typically scheduled when you're due for your next weekly KwikPen injection. They may suggest a dose increase if you're not yet on the maximum 15 mg dose. Moving from one dose to the next (for example, from 5 mg to 7.5 mg) can restart weight loss progress in some people, though individual responses vary.
Alongside medication, examine your lifestyle: are you maintaining the reduced-calorie diet and increased physical activity that Mounjaro works best alongside? Sometimes a plateau simply means your current habits have stabilised your weight — small adjustments to diet or exercise may help shift the plateau. You can also track your progress using our free progress tracker to identify patterns in your weight over time. A plateau of a few weeks is normal and doesn't mean treatment has failed.
- 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.
Is it normal for weight loss to stop on Mounjaro after a few weeks?
Yes, weight loss plateaus are normal. Your body adapts to the medication over time, and the rate of weight loss naturally slows. This doesn't mean Mounjaro has stopped working — it may mean your current dose needs adjusting or lifestyle factors need reviewing. Discuss this with your prescriber.
Should I increase my Mounjaro dose if weight loss has stopped?
Only if your prescriber recommends it. Dose increases happen gradually — each dose typically continues for at least 4 weeks before escalation. If you're not yet on 15 mg, your prescriber may suggest moving to the next dose level. Never adjust your KwikPen dose yourself without clinical guidance.
How long does a weight loss plateau usually last on Mounjaro?
Plateaus vary — some last 2–3 weeks, others longer. If your weight remains stable for more than 4 weeks despite being on a therapeutic dose and maintaining lifestyle changes, contact your GP. They can assess whether a dose adjustment or other support would help.
Can I use our GLP-1 weight loss calculator if weight loss has plateaued?
Yes. Our GLP-1 weight loss calculator can help you see projected outcomes at different doses, which may help you understand what to discuss with your prescriber about dose adjustment or whether a plateau is expected at your current dose level.
What if I'm on the maximum Mounjaro dose of 15 mg and weight has still stopped?
If you're on 15 mg weekly and weight loss has plateaued completely for several weeks, discuss this with your prescriber. They may review whether this is a natural plateau point, whether lifestyle factors have changed, or whether this medication is the right choice. Rarely, people don't respond well to Mounjaro — your GP can discuss alternatives.
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.