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
Weight Loss Plateau On Mounjaro — Why It Happens
A weight loss plateau on Mounjaro is a common experience where weight loss slows or stops despite continuing the injection. This can happen for several reasons, and it's not a sign that the medication has stopped working. Understanding why plateaus occur and what to do about them can help you stay motivated and make informed decisions with your GP or prescriber about your next steps.
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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 are a normal part of any weight loss journey, whether with or without medication. When you lose weight, your body adapts—your metabolic rate may decrease slightly as you have less body mass to maintain. Additionally, as you progress through dose titration on Mounjaro (starting at 2.5 mg and escalating up to 15 mg), your body may become accustomed to each dose level. Plateaus can also reflect the natural pattern of weight loss: initial rapid loss (often including water weight) followed by slower, more sustainable loss.
- Body adaptation as weight decreases
- Metabolic adjustment to lower body weight
- Calorie intake creeping up gradually
- Reduced physical activity levels
- Individual biological variation in response to the medication
Clinical trials show that Mounjaro helps participants lose an average of 15–21% of body weight on average, but individual results vary significantly. Some people experience steady loss throughout treatment, while others experience plateaus before resuming 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 to Do If You Hit a Weight Loss Plateau
If weight loss has stalled, discuss this with your prescriber before making changes. They may suggest increasing your Mounjaro dose if you have not yet reached the maximum (15 mg weekly). Dose increases should follow the standard titration schedule—minimum 4 weeks at each dose level before escalating.
Beyond medication, review lifestyle factors: ensure you are maintaining a reduced-calorie diet (plateaus often occur when calorie intake gradually increases), increase physical activity, and check that you are taking the weekly weight loss injection consistently. Our free GLP-1 weight loss calculator can help you track projected outcomes at different doses. Keep a progress log using our progress tracker to identify patterns in your weight, appetite, and energy levels over weeks rather than focusing on daily fluctuations.
- 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 does a weight loss plateau on Mounjaro typically last?
Plateaus vary greatly—some last 2–3 weeks, others longer. This is normal and does not mean the medication has stopped working. Continue your current dose, maintain your dietary and activity changes, and discuss duration with your prescriber if concerned.
Should I increase my Mounjaro dose if I hit a plateau?
Do not adjust your dose without prescriber guidance. If you have not yet reached 15 mg, your prescriber may recommend a dose increase after you have been on your current dose for at least 4 weeks. Discuss your plateau at your next review.
Can I take a higher dose of Mounjaro to break through a plateau?
The maximum Mounjaro dose is 15 mg once weekly. If you are not yet on this dose, a prescriber-guided increase may help. If you are already on 15 mg, dose escalation is not an option—focus on lifestyle factors instead.
Is it normal to have a weight loss plateau with a weekly weight loss injection?
Yes, plateaus are very common with GLP-1 and GIP/GLP-1 medications like Mounjaro. They reflect your body's natural adaptation and do not indicate treatment failure. Most people experience periods of slower loss interspersed with resumption of weight loss.
How do I know if Mounjaro is still working if my weight has stopped changing?
Beyond the scale, assess appetite control, energy levels, and how clothes fit. These often improve even when weight loss plateaus temporarily. Use our free progress tracker to log non-scale victories alongside weight. Discuss continued suitability of the medication with your prescriber at your regular reviews.
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.