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 Have I Stopped Losing Weight on Mounjaro?
Weight loss plateaus are common when taking Mounjaro, and there are several reasons why this happens. It doesn't mean the medication has stopped working—it often reflects your body adapting or indicates that lifestyle adjustments may help. Understanding the difference between a temporary plateau and a genuine loss of effectiveness is important for managing your expectations and knowing when to speak to your prescriber. This guide explains what's normal and what to do next.
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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.
Common Reasons for Weight Loss Plateaus on Mounjaro
A weight loss plateau occurs when your body reaches a new equilibrium despite continuing Mounjaro. Several factors explain this:
- Dose adaptation: Your body becomes accustomed to your current Mounjaro dose. This is normal—many people find that increasing to the next dose (following prescriber guidance) renews weight loss momentum.
- Reduced appetite effect: The appetite-suppressing effects of Mounjaro may lessen over time as your body adapts, though the medication continues to work at a metabolic level.
- Calorie creep: Portion sizes may gradually increase as nausea lessens, or food choices may shift without realisation—tracking intake via our free progress tracker can help identify this.
- Metabolic adaptation: Your metabolism adjusts to your lower weight, requiring a greater calorie deficit to continue losing weight. This is a natural physiological response.
- Lifestyle changes: Changes in physical activity, sleep quality, or stress levels can affect weight loss, independent of the medication.
Clinical trials show that weight loss typically continues at different doses—dose escalation is standard practice and is built into the Mounjaro treatment plan.
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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 to Do If Your Weight Loss Has Stalled
If you've stopped losing weight on Mounjaro, speak to your prescriber first—do not increase your dose yourself. Your prescriber will review your current dose, how long you've been on it, and whether escalation is appropriate. In the meantime, assess your lifestyle: use our BMI calculator to track your overall health metrics, review your diet honestly (are portions creeping up?), and check whether physical activity has changed. Even modest increases in movement or dietary adjustments can restart progress. Remember that a plateau lasting a few weeks is common and doesn't indicate failure—sustained plateaus lasting 8+ weeks may warrant a prescriber conversation about dose adjustment.
- 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 to stop losing weight while on Mounjaro?
Yes, weight loss plateaus are very common. Your body adapts to your current dose, and your metabolism adjusts to your lower weight. This doesn't mean Mounjaro has stopped working. Many people find that progressing to the next dose (following prescriber guidance) restarts weight loss. A plateau lasting a few weeks is typical; if it persists beyond 8 weeks, discuss with your prescriber.
Will increasing my Mounjaro dose restart weight loss?
Possibly, but dose increases must be prescribed by your healthcare provider—never adjust your dose yourself. Mounjaro is designed for gradual dose escalation (typically every 4 weeks), and clinical trials show that higher doses support continued weight loss. Your prescriber will assess whether you're ready to progress based on your current dose duration and tolerance.
What's the difference between a plateau and the medication stopping working?
A plateau is temporary stalling despite continuing the medication—this is normal and expected. The medication "stopping working" would mean no weight loss for many months at maximum dose with no underlying cause. Most plateaus resolve with dose adjustment, lifestyle tweaks, or simply waiting a few more weeks. Your prescriber can help distinguish between the two.
How long should I stay on one Mounjaro dose before expecting dose escalation?
The standard guidance is to remain on each dose for a minimum of 4 weeks before escalating. However, your prescriber may keep you on a dose longer if you're experiencing side effects or continuing to lose weight. The typical escalation schedule progresses from 2.5 mg → 5 mg → 7.5 mg → 10 mg → 12.5 mg → 15 mg, each separated by 4+ weeks.
Can lifestyle changes alone restart weight loss on Mounjaro?
Absolutely. Many people find that reviewing their diet (using our free progress tracker), increasing physical activity, improving sleep, or reducing stress restarts progress without needing a dose increase. A weekly weight loss injection like Mounjaro works best alongside reduced-calorie intake and increased movement—medication alone is not a substitute for these lifestyle factors.
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.