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
Dumping Syndrome and Mounjaro: What You Need to Know
Dumping syndrome is a potential side effect that can occur with GLP-1 and dual GIP/GLP-1 weight loss medications like Mounjaro (tirzepatide) and Wegovy (semaglutide). This guide explains what dumping syndrome is, how it relates to these prescription weight loss injections, and how Mounjaro compares to Wegovy in terms of this and other gastrointestinal effects. Both medications work by slowing how quickly food leaves your stomach, which can trigger dumping syndrome symptoms in some people. Understanding the differences between these two medications can help you and your GP make an informed decision about which might be suitable for you.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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 Mounjaro and Wegovy Affect Stomach Emptying
Dumping syndrome occurs when food moves too quickly from the stomach into the small intestine, causing symptoms like nausea, dizziness, heart palpitations, and diarrhoea. Mounjaro (tirzepatide) and Wegovy (semaglutide) both slow gastric emptying as part of how they help with weight loss — which is why dumping-like symptoms can sometimes occur early in treatment.
However, this effect typically reduces over time as your body adapts. The key difference: Mounjaro is a dual GIP and GLP-1 receptor agonist, while Wegovy activates only the GLP-1 pathway. In clinical trials (SURMOUNT for Mounjaro, STEP for Wegovy), gastrointestinal side effects were common initially but improved substantially by weeks 12–16 as patients continued treatment. Nausea and diarrhoea rates declined as the body adjusted.
- Mounjaro: dual mechanism may cause slightly different GI symptom patterns than single GLP-1 agents
- Wegovy: single GLP-1 mechanism, well-established trial data on symptom resolution timelines
- Both: symptoms typically peak in weeks 1–4, improve by weeks 8–12 with continued use
Clinically BackedWeight Loss
No appointments. No waiting rooms. Just care — from a UK-regulated online pharmacy.
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.
Which Medication Might Be Right for You?
Neither Mounjaro nor Wegovy is inherently "better" for dumping syndrome risk — individual response varies significantly. Your suitability depends on your personal medical history, any existing stomach or digestion problems, other medications you take, and how your body responds during the initial titration phase. If you have a history of severe gastroparesis or acute pancreatitis, your prescriber may recommend additional monitoring or an alternative approach.
Both medications require a prescription and clinical assessment from a licensed healthcare professional. Your GP or private prescriber will review your full health picture before recommending which medication suits you best. If you experience persistent dumping syndrome symptoms during the first 4–8 weeks, report them to your prescriber — dose adjustment or a switch between medications may help. Use our free GLP-1 weight loss calculator to explore projected outcomes, and track your progress and any symptoms with our free progress tracker as you begin treatment.
- 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.
What exactly is dumping syndrome?
Dumping syndrome is when food moves too quickly from your stomach into your small intestine, causing symptoms like nausea, dizziness, sweating, palpitations, and diarrhoea. It can occur with GLP-1 and GIP/GLP-1 medications because they slow stomach emptying — when your body adjusts, these symptoms usually improve within 4–8 weeks.
Is dumping syndrome more common with Mounjaro or Wegovy?
Both medications can cause dumping-like symptoms early in treatment. Mounjaro and Wegovy show similar rates of gastrointestinal side effects in clinical trials. Individual response varies greatly — some people experience no symptoms, others experience mild nausea or diarrhoea. Your prescriber can help determine which is more suitable based on your health history.
Does dumping syndrome from these medications go away?
Yes, in most cases. Clinical trial data shows that nausea, diarrhoea, and stomach discomfort typically peak in weeks 1–4, then improve substantially by weeks 8–12 as your body adapts to the medication. If symptoms persist beyond 12 weeks, contact your prescriber for guidance.
Can I switch from Mounjaro to Wegovy if I get dumping syndrome symptoms?
Possibly, but this decision must be made with your prescriber. Switching medications changes your GIP/GLP-1 signalling pathway, which may alter your symptom pattern. Many people find their symptoms improve naturally as they continue on the same medication, so your prescriber may recommend waiting 8–12 weeks before considering a switch.
What can I do to manage dumping syndrome symptoms while on Mounjaro or Wegovy?
Eat smaller meals, avoid high-sugar foods and drinks, stay hydrated, and eat slowly. These lifestyle adjustments often help reduce symptoms during the first few weeks. Avoid lying down immediately after eating. If symptoms are severe or persistent, contact your GP — they may recommend temporary dose reduction or additional support.
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.