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
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Why Weight Loss Stalls on Mounjaro
Weight loss plateaus are common when taking Mounjaro (tirzepatide), and they don't mean the medication has stopped working. If you're stalling on Mounjaro after an initial period of weight loss, several factors could be involved—from your body adapting to the medication, to dietary habits shifting, or needing a dose increase. This guide explains what happens during a weight loss plateau, why it occurs, and practical steps you can take within the NHS framework to move forward. Understanding the difference between a temporary stall and a true plateau will help you decide whether to adjust your approach or speak 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.
Understanding Weight Loss Plateaus on Mounjaro
A weight loss plateau occurs when your body reaches a new equilibrium—the calories you're consuming balance with the calories you're burning. This is a normal part of weight loss and doesn't mean Mounjaro has stopped working. Your body adapts to medications over time, and initial gradual weight management often slows naturally. Typical plateau timing: most people experience slowing after 12–16 weeks, though this varies. If you're on Mounjaro through NHS specialist tier 3 services, your prescriber will monitor your progress and may recommend a dose titration (increasing to the next dose level) if you've been stable on your current dose for several weeks.
- Initial weight loss is often faster due to reduced appetite and food intake changes
- After 8–12 weeks, your metabolism adjusts and loss typically slows to 0.5–1 kg per week
- A plateau lasting 3–4 weeks without any weight change may warrant review
- Dose increases on Mounjaro can occur every 4 weeks up to a maximum of 15 mg weekly
Important: if you're accessing Mounjaro privately, you should also have regular check-ins with your prescriber about plateau management—this is part of responsible prescribing.
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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.
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Practical Steps to Address Plateaus
If you're stalling, assess your lifestyle first. Review your diet: measure portions, log food intake for a week, and check whether portion sizes have gradually increased. Mounjaro may reduce appetite, but you still need to maintain a calorie deficit to continue losing weight. Increase physical activity if possible—even 10–15 minutes of daily walking or light strength training can help. Track your progress using tools like our free progress tracker, which helps you spot trends beyond just weight (energy levels, how clothes fit, measurements). Speak with your GP or NHS prescriber about whether a dose increase is appropriate. Your prescriber may suggest remaining on your current dose longer, increasing to the next dose level (minimum 4 weeks per dose), or reviewing whether other factors like sleep, stress, or medication interactions are affecting results.
- 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 long should I wait before thinking my weight loss has truly stalled?
Three to four weeks without any weight change (on the scale or in measurements) typically signals a plateau worth addressing. However, weight fluctuates daily due to water retention, food intake, and hormones. Use our free progress tracker to spot longer-term trends. If you've been on your current Mounjaro dose for 4+ weeks with no change, discuss this with your prescriber at your next appointment.
Can I increase my Mounjaro dose myself if I'm stalling?
No—Mounjaro dose increases must be managed by your prescriber following a clinical assessment. Each dose increase should be spaced at least 4 weeks apart, with a maximum dose of 15 mg weekly. Your prescriber will decide whether you're ready to increase based on how well you're tolerating your current dose, side effects, and weight loss progress.
Does stalling on Mounjaro mean it's not working anymore?
Not necessarily. A plateau is a normal part of weight loss, not medication failure. Mounjaro continues to work by reducing appetite and supporting calorie control. However, your body adapts over time, and environmental factors like diet changes or increased stress can affect results. Your prescriber can review whether you'd benefit from a dose increase or lifestyle adjustments.
What's the difference between Mounjaro and Wegovy for plateaus?
Both are effective weight loss medications, but Mounjaro is a dual GIP and GLP-1 agonist while Wegovy (semaglutide) is a GLP-1 agonist only. Clinical trials show Mounjaro may support slightly greater average weight loss. Plateau management is similar for both—discuss with your prescriber whether your current dose is optimal or if adjustment is needed.
Should I exercise more if I'm stalling on Mounjaro?
Adding or increasing physical activity can support weight loss, especially if your diet is already well-managed. However, don't drastically increase exercise without reviewing your overall energy and nutrition first. Aim for sustainable increases—30 minutes of moderate activity most days is a good target. Combine this with dietary review and speak to your prescriber about dose optimization.
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.