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 Has My Weight Loss Stopped On Mounjaro?
Weight loss plateaus are common when taking Mounjaro (tirzepatide), even when the medication is working correctly. Your body may reach a new equilibrium where your current dose is balanced against your food intake and activity level. This doesn't mean Mounjaro has stopped working — it often means your body has adapted. Understanding why plateaus happen, when they're normal, and what options exist can help you decide your next steps with your GP or prescriber.
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Calculate Your BMI Instantly
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 (tirzepatide) happen for several evidence-based reasons. Your body adapts to the medication over time, and appetite suppression effects may stabilise — this is physiologically normal. As you lose weight, your calorie requirements decrease, so the same dietary intake that created a deficit before may no longer do so. Additionally, if you've been on the same dose for several weeks without further loss, your prescriber may consider dose titration — gradually increasing to the next level (up to the maximum 15mg weekly injection). Other factors include reduced physical activity, increased food intake without realising, hormonal changes, or underlying medical conditions like thyroid disorders. The NHS recommends discussing persistent plateaus with your GP, especially if you've been stable for 4+ weeks. Our GLP-1 weight loss calculator can help you understand where your current dose sits in the expected range.
- Body adaptation to medication effects
- Reduced calorie deficit as weight decreases
- Insufficient dose escalation (still on early doses)
- Lifestyle factors: diet creep, reduced activity
- Medical causes: thyroid, hormones, medications
Clinically BackedWeight 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 Your Weight Loss Has Plateaued
If your weight loss has stopped, speak with your GP or the prescriber managing your Mounjaro. They can assess whether you're on an optimal dose — many people haven't yet reached their maximum dose of 15mg, meaning further escalation is possible. A prescriber may also review your dietary intake and physical activity, as weight loss injections work alongside lifestyle changes, not instead of them. Track your progress using our free progress tracker to identify genuine plateaus (no loss for 4+ weeks) versus normal fluctuations. If you're on a stable dose and have lost significant weight already, a plateau may reflect your new healthier weight — discussing this with your prescriber helps clarify whether continuing is appropriate for your individual goals.
- 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 normal on Mounjaro?
Yes, plateaus are very common and don't mean Mounjaro has stopped working. Your body adapts to the medication, and your calorie requirements decrease as you lose weight. This is physiologically normal. Many people continue losing weight after a plateau, especially with dose adjustments or lifestyle changes.
How long should I wait before contacting my GP about a plateau?
If you've seen no weight change for 4 or more weeks, it's reasonable to contact your prescriber. They can assess whether dose escalation is appropriate or review other factors affecting your progress. Don't wait months — early discussion helps clarify the best next steps.
Can my Mounjaro dose be increased if I've plateaued?
Yes, if you haven't reached the maximum 15mg weekly dose, your prescriber may consider escalating to the next dose level. Each dose increase requires a minimum of 4 weeks before escalating further. Your GP or specialist will assess whether escalation is appropriate based on your individual response and health status.
Does a weight loss plateau mean I should stop taking Mounjaro?
Not necessarily. A plateau doesn't mean the medication has failed — it often means your body has adapted to your current dose. Dose escalation, dietary review, or increased activity may restart progress. Your prescriber can help decide whether continuing is right for you.
What lifestyle changes help break a weight loss plateau on Mounjaro?
Reviewing calorie intake (many people unknowingly eat more after initial weight loss), increasing physical activity, ensuring adequate protein intake, and managing stress and sleep can all help. Mounjaro works best alongside a reduced-calorie diet and increased physical activity — medication alone isn't sufficient for sustained results.
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.