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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What Happens If You Stop Mounjaro?
If you stop taking Mounjaro (tirzepatide), you can expect your appetite to gradually return to normal and any weight loss achieved during treatment may start to reverse over time. How quickly this happens varies between individuals — some people maintain weight loss for several months, while others see weight return more quickly. This is why Mounjaro is not a one-off treatment but part of an ongoing weight management strategy. Always discuss stopping Mounjaro with your GP or prescriber rather than stopping abruptly, as they can advise on the safest approach for your individual circumstances.
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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.
How Your Body Responds After Stopping
When you stop Mounjaro, the medication leaves your system gradually. Tirzepatide has a half-life of approximately 4–5 days, meaning it takes about a week to clear most of the drug from your body. As the medication wears off, the dual GIP and GLP-1 signalling that suppressed your appetite will stop, and your natural hunger hormones return to baseline. This means appetite typically increases again within 1–2 weeks of stopping.
Clinical trial data shows that people who discontinue GLP-1 or GIP/GLP-1 medications often experience:
- Return of appetite to pre-treatment levels
- Increased cravings for foods that were previously easy to avoid
- Reduced feeling of fullness after meals
- Potential weight regain if diet and exercise patterns revert to pre-treatment habits
Weight regain is not assured — many people who have established sustainable lifestyle changes during Mounjaro treatment can maintain their weight loss long-term, even after stopping. The key factor is whether dietary and physical activity changes have become your permanent new routine.
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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.
Stopping Mounjaro Safely — What Your GP Should Know
Never stop Mounjaro abruptly without speaking to your prescriber. Your GP or specialist may recommend gradually reducing your dose rather than stopping immediately, though abrupt cessation is not medically dangerous — it simply means faster appetite return and greater rebound risk.
Before stopping, discuss with your healthcare team:
- Whether you can maintain the lifestyle changes you've made (diet and exercise)
- If you have weight-related health conditions (diabetes, high blood pressure) that may worsen with weight regain
- Whether continuing Mounjaro long-term might be more appropriate for you
- Strategies to manage appetite if you do stop
Current NHS guidance and NICE recommendations suggest that for people with significant obesity or weight-related health conditions, ongoing pharmacological support may be more effective than stopping medication once weight loss is achieved.
- 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.
Will I regain all the weight I lost if I stop Mounjaro?
Not necessarily. Weight regain depends entirely on whether you maintain the dietary and physical activity changes you made during treatment. Many people who have established sustainable eating and exercise habits keep weight off long-term. However, without Mounjaro's appetite-suppressing effects, maintaining a calorie deficit becomes harder, so some weight regain is common. Your GP can help you plan strategies to minimise regain.
How quickly will my appetite come back after stopping Mounjaro?
Appetite typically begins returning within 1–2 weeks as Mounjaro clears your system. The medication has a half-life of 4–5 days, so it takes roughly a week for most to leave your body. For some people appetite returns gradually, for others it returns quite quickly. Individual variation is significant — some people maintain better appetite control than others after stopping.
Can I restart Mounjaro if I regain weight after stopping?
Yes, you can restart Mounjaro if you regain weight and your prescriber agrees it's clinically appropriate. However, restarting requires a new clinical assessment and prescription — it's not automatic. Your prescriber will reassess your eligibility based on your current weight, BMI, and health conditions. Discuss this option with your GP or private prescriber before stopping if you're concerned about regain.
Should I stop Mounjaro gradually or all at once?
Stopping abruptly is medically safe — the medication will clear naturally over about a week. However, your prescriber may recommend gradual dose reduction to give your body and appetite time to adjust. There's no medical benefit to tapering for this medication (unlike some others), but some people find gradual stopping easier psychologically. Discuss your preference with your GP.
What's the difference between stopping Mounjaro and stopping Wegovy?
Both medications are weight management injections with similar effects on appetite and weight. Mounjaro is a dual GIP and GLP-1 agonist (tirzepatide), while Wegovy is a GLP-1 agonist (semaglutide). When stopped, both show similar patterns: appetite returns and weight regain is possible if lifestyle hasn't changed. The main difference is that Mounjaro may show slightly faster initial effects during treatment, but stopping outcomes are comparable. ```
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