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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Can Mounjaro Make You Vomit?
Yes, Mounjaro (tirzepatide) can cause nausea and vomiting, particularly during the early weeks of treatment or when your dose increases. These are among the most frequently reported side effects in clinical trials. However, most people find that nausea improves significantly over time as their body adjusts to the medication. Understanding what to expect, how to manage symptoms, and whether this medication is right for you requires proper clinical assessment through a qualified prescriber in the UK. This guide explains the evidence and provides practical context for anyone considering this treatment.
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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.
Mounjaro Nausea and Vomiting: What the Evidence Shows
Nausea is the most common side effect of Mounjaro, affecting more than 1 in 10 people in clinical trials. Vomiting is also reported but less frequently than nausea. Both typically occur in the first few weeks of starting treatment or when increasing to a higher dose.
- Very common side effects (affecting more than 1 in 10 people): nausea, vomiting, diarrhoea, constipation, and stomach pain
- When symptoms peak: Usually within the first 2–4 weeks, then gradually improve as your body adapts
- Dose titration matters: Mounjaro starts at 2.5 mg and increases gradually (minimum 4 weeks per dose level), which helps reduce the intensity of nausea compared to starting at a higher dose
- Individual variation: Some people experience mild symptoms, others more severe; age, weight, and medication tolerance all play a role
If nausea persists or is severe, your prescriber may recommend staying on your current dose longer, adjusting your diet, or in some cases, reassessing whether this medication is suitable for you.
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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.
Accessing Mounjaro in the UK: NHS vs Private Routes and What It Costs
NHS access: Mounjaro may be available through specialist tier 3 weight management services, though availability varies significantly by region and waiting times can be lengthy. Your GP can refer you to a specialist service if you meet eligibility criteria (BMI 30+ or 27–29.9 with weight-related health conditions).
Private prescription route: Mounjaro is available through UK-licensed online prescribers following a clinical assessment. Most private prescriptions cost between £129–£320 per month depending on your dose, with costs typically higher for the maximum 15 mg dose. A Mounjaro KwikPen device contains 4 weekly doses. Online consultations usually take 10–15 minutes and are conducted with UK-registered doctors or specialist prescribers.
Whether NHS or private, any prescriber will assess your eligibility, medical history, and suitability before issuing a prescription. If nausea is a concern, discuss this during your consultation.
- 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 nausea from Mounjaro go away?
Yes, for most people nausea improves significantly within 2–4 weeks as your body adjusts. However, it may return temporarily when you increase to a higher dose. If nausea persists beyond 4 weeks or is severe, contact your prescriber. Staying hydrated, eating small frequent meals, and avoiding fatty foods can help manage symptoms.
Can I take anti-sickness medication with Mounjaro?
Some anti-sickness medications can be used, but always check with your prescriber first. Do not assume over-the-counter remedies are safe to combine with Mounjaro. Your GP or prescriber can recommend options that work safely alongside your tirzepatide treatment.
What should I eat if Mounjaro makes me feel sick?
Stick to bland, easy-to-digest foods: plain toast, crackers, boiled rice, soup, and ginger tea. Avoid fatty, spicy, or strong-smelling foods. Eat smaller, more frequent meals rather than large ones. Many people find that eating too quickly or too much triggers nausea, so slow down and pause between bites.
How much does Mounjaro cost on the NHS?
If prescribed through NHS specialist services, Mounjaro is free at the point of care (standard NHS prescription charge applies). However, NHS availability is limited and regional. Private prescriptions typically range from £129–£320 monthly depending on your dose, plus the cost of ongoing consultations or monitoring.
Is Mounjaro the same as Wegovy?
No. Both are prescription-only weight management injections, but Mounjaro (tirzepatide) is a dual GIP/GLP-1 agonist, while Wegovy (semaglutide) is a GLP-1 agonist only. Mounjaro may produce larger average weight loss in clinical trials, but both can cause nausea. Your prescriber can discuss which is more suitable for you.
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.