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 (tirzepatide), even when following a reduced-calorie diet and exercising regularly. This happens because your body adapts to the medication over time, a natural physiological response called tolerance. Several factors can influence whether you continue to lose weight, including your current dose, how long you've been taking it, dietary habits, and physical activity levels. Understanding what's happening and knowing your options can help you move forward with your healthcare team.
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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
Weight loss plateaus on Mounjaro occur for several evidence-based reasons. Your body may have adapted to your current dose — as a weekly weight loss injection, Mounjaro's effectiveness can stabilise after several weeks or months as your system adjusts. If you've been on the same dose for more than 4 weeks without weight loss, your prescriber may recommend a dose titration — increasing to the next strength. Other factors include: reduced adherence to diet and exercise changes, which are essential alongside medication; increased calorie intake without realising it; or reaching a natural plateau where your body settles at a new weight. Some people also experience adaptation where appetite suppression effects diminish slightly over time, even though the medication is still working. Additionally, if you've lost a significant amount of weight already, your metabolism has adjusted, meaning you need a larger calorie deficit to continue losing at the same rate. Track your progress using our free progress tracker to identify patterns and discuss them with your GP or prescriber.
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.
UK Access Routes and Cost Context for Continuing Treatment
In the UK, Mounjaro is accessed through two main routes: NHS specialist weight management services (through tier 3 or 4 services) or private prescription via a UK-licensed prescriber. NHS access is free at the point of delivery but availability varies significantly by region and waiting times can be lengthy. Private prescription costs vary depending on your dose and provider — weight loss injections typically range from £150 to £300+ per month depending on the strength you're prescribed. Before considering cost, calculate your potential results using our GLP-1 weight loss calculator to understand realistic expectations at different doses. If you're on the NHS, your prescriber will manage dose adjustments at specialist appointments. If accessing privately, an online consultation with a UK prescriber allows assessment and dose adjustment recommendations based on your progress and response to treatment.
- 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 a weight loss plateau on Mounjaro permanent?
No. A plateau typically means your body has adapted to your current dose. Most prescribers recommend staying at your dose for at least 4 weeks before increasing, as weight loss may resume. If it doesn't, dose titration to a higher strength (up to 15 mg maximum) often restarts weight loss. Individual responses vary significantly.
Should I increase my dose if I've stopped losing weight?
Never adjust your Mounjaro dose yourself. Contact your prescriber or GP. They'll assess whether a dose increase is appropriate based on your current weight, health, and how long you've been at your present dose. Minimum 4 weeks between dose increases is standard guidance.
Can I switch from Mounjaro to Wegovy if I'm not losing weight?
A switch between medications is possible but must be managed by your prescriber — it's not a simple switch. Mounjaro (dual GIP + GLP-1 agonist) and Wegovy (GLP-1 only) work differently. Your prescriber will assess whether a change is appropriate for you based on individual circumstances.
What should I discuss with my GP about my weight loss plateau?
Bring a record of your weight over the past 8–12 weeks (our progress tracker can help), note any changes in diet or exercise, list all medications you're taking, and mention any side effects. Discuss whether increasing your dose, adjusting lifestyle, or other options might help restart progress.
Does Mounjaro stop working, or is it always about lifestyle changes?
Mounjaro doesn't "stop working," but your body adapts to it. The medication and lifestyle changes work together — without reducing calories and moving more, medication alone is less effective. If you've maintained good habits and plateaued, dose adjustment may help. Your GP can help determine the best approach for your situation.
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.