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 Gain After Stopping Mounjaro — What the Evidence Shows
When you stop taking Mounjaro (tirzepatide), some people experience weight regain — this is an important consideration when starting treatment. Unlike a supports, Mounjaro is a prescription weight loss injection that works while you're taking it, and weight can return if treatment stops without sustained lifestyle changes. Understanding what to expect, and how this compares to stopping Wegovy (semaglutide), helps you make an informed decision with your prescriber. Evidence from clinical trials and real-world use gives us clear insights into post-treatment weight patterns for both medications.
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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.
Weight Regain: SURMOUNT vs STEP Trial Data
Clinical trials for both Mounjaro and Wegovy included follow-up periods after treatment stopped, revealing important differences in weight regain patterns. In the SURMOUNT trials, participants who continued Mounjaro maintained their weight loss, while those who discontinued showed gradual weight return over weeks and months — though not always back to baseline. The STEP trials with Wegovy (semaglutide) showed a similar pattern: weight regain occurred after stopping, but the rate and total regain varied by individual.
Key differences in mechanism: Mounjaro is a dual GIP and GLP-1 receptor agonist, while Wegovy is a GLP-1 agonist only. This dual action in Mounjaro may theoretically affect how quickly appetite signals return and how metabolism resets after stopping, but clinical data directly comparing post-treatment regain between the two is limited. Both weekly weight loss injections require ongoing use to maintain results — they are management tools, not permanent solutions.
Individual factors like diet adherence, physical activity, and baseline metabolism significantly influence how much weight returns and how quickly.
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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.
Managing Weight After Treatment — Prescriber Guidance
Your prescriber will discuss what happens when you stop treatment before you start Mounjaro or Wegovy. The goal is to use the weight loss period to establish sustainable eating and activity habits that support long-term weight maintenance. Some UK prescription weight loss services recommend transitioning to lower doses rather than stopping abruptly — this allows your body to adjust gradually and may reduce rapid appetite rebound.
Planning for sustainability: Use our free GLP-1 weight loss calculator to understand potential weight loss projections, and our progress tracker to monitor changes once you've achieved your goal. Many people continue some form of structured diet or activity support after stopping medication. Restarting Mounjaro is also an option if weight regain becomes significant — your prescriber can reassess eligibility and discuss whether continued or intermittent treatment suits your individual situation.
- 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.
Does weight always come back after stopping Mounjaro?
Not always completely. Weight regain varies significantly between individuals. Clinical trials show some people maintain most of their loss if lifestyle changes (diet and activity) are sustained. Others regain gradually over weeks to months. Your baseline health, metabolism, and adherence to new eating habits are key factors.
Is weight regain after Mounjaro worse than after Wegovy?
Evidence suggests regain patterns are similar between both medications — most weight returns gradually rather than suddenly. Mounjaro's dual mechanism theoretically could affect regain differently, but direct head-to-head trial data comparing post-treatment weight patterns is limited. Individual variation is significant regardless of medication.
Can I restart Mounjaro if I regain weight after stopping?
Yes. Restarting is possible and your prescriber can reassess your suitability. Some people use weight loss injections intermittently or cyclically — stopping temporarily and restarting if needed. This is a decision to discuss with your GP or specialist as part of your ongoing management plan.
How long after stopping does weight gain happen?
Weight regain typically begins within days to weeks of stopping, as appetite-regulating hormone signals gradually normalise. The pace varies — some people notice changes within 1–2 weeks, others over several weeks or months. Maintaining reduced calorie intake and activity levels can slow or minimise regain.
Should I plan to take Mounjaro long-term to avoid weight regain?
This is a personal decision in discussion with your prescriber. Some people take Mounjaro long-term, others use it for a defined period to establish habits, then stop. Your prescriber will consider your individual health, regain risk, eligibility (BMI ≥30 or ≥27 with comorbidities), and preference when planning treatment duration.
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.