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
What Happens to Side Effects When You Stop Mounjaro?
If you're experiencing side effects from Mounjaro (tirzepatide), you may be wondering what happens when you stop taking it. Most gastrointestinal side effects like nausea, constipation, and stomach pain typically improve within days to weeks after your last injection. However, stopping should always be discussed with your prescribing GP or specialist, as discontinuing suddenly may have other health effects—especially if you're managing weight or blood sugar levels. This guide explains the timeline, what to expect, and how to stop safely.
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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.
How Quickly Do Mounjaro Side Effects Resolve?
Side effects from Mounjaro vary in how quickly they resolve after stopping. Nausea and vomiting typically improve within 3–7 days as the medication leaves your system. Constipation and diarrhoea may take 1–2 weeks to normalise as your gut adjusts. Appetite suppression often returns to baseline within 1–2 weeks, though some people notice hunger returning more suddenly. Injection site reactions resolve immediately once injections stop. Other effects like fatigue or headaches usually improve within 7–14 days. Importantly, the tirzepatide dose titration process means your body has been adapting gradually—stopping suddenly can sometimes cause these symptoms to fluctuate unpredictably. For this reason, your GP may recommend spacing out your final doses rather than stopping abruptly, particularly if you've been on a higher dose like 10mg, 12.5mg, or 15mg. Always discuss your individual timeline with your prescriber before stopping.
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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.
Important Considerations Before Stopping Mounjaro
Weight rebound is a key consideration. Research shows that weight typically returns over several months after stopping GLP-1 or GIP/GLP-1 medication, sometimes within weeks. This doesn't mean Mounjaro "failed"—it reflects how the medication was supporting your weight management. Your prescriber may discuss alternatives like Wegovy (semaglutide), which is the licensed GLP-1 alternative, or lifestyle strategies to maintain your progress. If you're stopping due to side effects, your GP can assess whether a lower dose or different medication suits you better. Stopping without a plan may result in rapid weight regain and frustration. Document which specific side effects prompted your decision—this information helps your GP recommend next steps, whether that's continuing at a lower dose, switching medication, or pausing treatment temporarily whilst adjusting other factors like diet or activity. Always consult your prescribing healthcare professional rather than stopping independently.
- 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 after stopping Mounjaro do side effects go away?
Most gastrointestinal side effects resolve within 1–2 weeks. Nausea typically improves within 3–7 days, whilst constipation or appetite changes may take longer. Some effects like fatigue resolve within 7–14 days. Individual timelines vary based on your Mounjaro dose and how long you've been taking it.
Will I regain weight after stopping Mounjaro?
Yes, weight typically returns after stopping GLP-1 or GIP/GLP-1 medication, often within weeks to months. This is normal and reflects how the medication was supporting your weight management. Discuss weight maintenance strategies with your GP before stopping, such as continuing lifestyle changes or considering alternative treatments.
Can I stop Mounjaro immediately or do I need to taper?
Always discuss stopping with your prescriber rather than stopping abruptly. Depending on your dose, your GP may recommend spacing out final injections rather than stopping suddenly. A gradual approach can help your body adjust more smoothly and prevent side effects from fluctuating unpredictably.
What should I do if Mounjaro side effects are unbearable?
Contact your prescriber immediately. Options include reducing your dose, pausing treatment temporarily, or switching to an alternative like Wegovy (semaglutide). Your GP can assess what's best for your individual health. Never stop without medical guidance, as your underlying health conditions may need alternative support.
Can I restart Mounjaro after stopping it?
Possibly, but this depends on your individual circumstances and why you stopped. Some people successfully restart at a lower dose if side effects were dose-related. Others may benefit from Wegovy or other approaches. Your prescriber will assess whether restarting is appropriate and safe for your health profile.
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.