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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I've Stopped Losing Weight on Mounjaro — What This Means
If you've been taking Mounjaro (tirzepatide) for several weeks and your weight has plateaued, you're not alone. Weight loss plateaus are common with weekly weight loss injection medications, and there are several reasons why this happens and steps you can take. This guide explains what to expect, when to seek GP advice, and how dose adjustments or lifestyle changes might help restart progress.
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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.
Why Weight Loss Plateaus Happen on Mounjaro
Weight loss plateaus on Mounjaro are a normal part of the weight management journey and typically occur for several reasons:
- Your body adapts to the medication. Over time, your body may become accustomed to the appetite-suppressing effects of tirzepatide, meaning the GIP and GLP-1 signals become less novel.
- You may not have reached your current dose maximum. Mounjaro uses dose titration — starting at 2.5 mg and increasing every 4 weeks up to a maximum of 15 mg. If you're not yet at the highest tolerated dose, your prescriber may recommend escalation.
- Calorie intake may have increased gradually. As nausea and appetite suppression reduce, it's easy to slowly increase portion sizes or frequency without realising.
- Physical activity may have decreased. Initial weight loss often comes from medication plus activity; reduced exercise can slow progress.
- Metabolic adaptation occurs. As you lose weight, your resting metabolic rate naturally decreases — your body requires fewer calories at a lower weight.
The SURMOUNT clinical trials showed that average weight loss continued across all dose levels, but individual timelines and plateaus vary considerably.
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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 noticed your weight hasn't changed for 4 weeks or more, consider these steps:
- Review your diet honestly. Track your food and drink intake for a few days — portion creep is common as side effects ease. Use our free weight converter and progress tracker to monitor patterns.
- Increase physical activity gradually. Even adding a 20-minute walk most days or increasing strength training can restart progress.
- Contact your GP or prescriber. If you're not yet at the maximum dose (15 mg), your prescriber may recommend dose escalation — only if you're not experiencing intolerable side effects.
- Rule out other factors. Hormonal changes, stress, sleep deprivation, and certain medications can affect weight loss. Your GP can assess these.
- Ensure consistent timing. Take your Mounjaro KwikPen on the same day each week — skipped doses can affect efficacy.
- 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. Weight plateaus are temporary. Dose increases, dietary adjustments, or increased activity often restart progress. Individual timelines vary, but most people see movement again within 2-4 weeks of making changes. Contact your prescriber if plateau lasts longer than 4-6 weeks.
Should I increase my Mounjaro dose myself if I've stopped losing weight?
No. Never adjust your dose without prescriber guidance. Each dose increase requires a 4-week minimum interval and must be assessed for tolerability. Your GP or prescriber will recommend escalation only if appropriate and safe for you.
Can I use a weekly weight loss injection alongside another medication?
This depends on your other medications. GLP-1 and GIP/GLP-1 medications can interact with some drugs — particularly oral contraceptives, diabetes medications, and certain gastric medications. Always inform your prescriber of all medications you take.
How long should I wait before contacting my GP about a weight plateau?
If your weight hasn't changed for 4-6 weeks despite no lifestyle changes, contact your GP. They can assess whether dose escalation, lifestyle adjustment, or investigation of other factors is appropriate.
Does Mounjaro stop working, or is a plateau just a temporary phase?
Mounjaro doesn't "stop working," but the appetite-suppressing effect may become less noticeable as your body adapts. This is why dose titration exists. With appropriate dose increases and lifestyle consistency, most people continue losing weight on prescription weight loss injections.
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.