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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How To Stop Feeling Sick On Mounjaro
Nausea is one of the most common side effects when starting Mounjaro (tirzepatide), affecting more than 1 in 10 people during the initial weeks. The good news is that nausea often improves as your body adjusts to the medication, and several practical strategies can help reduce how sick you feel. This guide covers evidence-based management techniques and explains how nausea on Mounjaro compares to other weight loss injections like Wegovy. If you're experiencing persistent sickness, always speak to your GP or the prescriber who issued your tirzepatide prescription.
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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.
Managing Nausea: Practical Strategies and Medication Differences
Nausea typically peaks in the first 2–4 weeks after starting Mounjaro or increasing your dose, then gradually improves as your body adapts. Practical steps to reduce sickness include:
- Eat smaller, more frequent meals instead of large portions — your stomach empties more slowly on tirzepatide
- Avoid fatty or greasy foods, which can trigger nausea more easily
- Stay hydrated with water and electrolyte drinks — dehydration worsens nausea
- Eat slowly and chew thoroughly before swallowing
- Take your injection at night so you sleep through the initial side effect period
- Ginger tea or ginger biscuits may help settle your stomach
Comparing Mounjaro and Wegovy: Both are GLP-1 type medications that slow gastric emptying, so both can cause nausea. Clinical trials show similar nausea rates — approximately 26% on Mounjaro and 25% on Wegovy experience nausea. The key difference is the mechanism: Mounjaro is a dual GIP and GLP-1 receptor agonist, while Wegovy is GLP-1 only. This dual action in Mounjaro may theoretically offer different symptom patterns between individuals, though nausea severity is comparable in trials. Your prescriber can discuss which medication might suit you better based on your individual tolerance.
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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.
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When To Contact Your GP and Dose Adjustment Options
Mild nausea that improves over a few days is a normal adjustment response. Contact your GP or prescriber urgently if: nausea is severe and persistent beyond 2 weeks, you cannot keep food or fluids down (risk of dehydration), or you experience severe stomach pain spreading to your back (possible pancreatitis sign). Your prescriber may suggest pausing your dose increase, staying on your current dose longer, or switching to an alternative weight loss injection if nausea remains unmanageable. Never stop Mounjaro abruptly — always discuss changes with your healthcare provider. Using our GLP-1 weight loss calculator can help you understand expected outcomes at different doses, which may inform conversations with your prescriber about dose adjustments if side effects are troublesome.
- 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 does nausea last on Mounjaro?
Nausea typically peaks in the first 1–2 weeks after starting or increasing your dose, then gradually improves over 3–4 weeks as your body adapts. Most people find nausea is mild or gone by week 4 of each dose level. If severe nausea persists beyond 2 weeks, contact your prescriber.
Is nausea worse on Mounjaro than Wegovy?
Clinical trials show similar nausea rates for both medications — approximately 26% on Mounjaro versus 25% on Wegovy. Individual experience varies significantly. Some people tolerate one better than the other, which is why your prescriber assesses suitability during your clinical assessment.
Can I take anti-nausea medication with Mounjaro?
Over-the-counter options like ginger or peppermint may help naturally. For prescription anti-nausea medication, always discuss with your GP or prescriber first — some medications may interact with tirzepatide or affect how your body absorbs other drugs.
Does eating less help with Mounjaro nausea?
Yes — smaller, more frequent meals are better tolerated than large portions. Since Mounjaro slows how quickly food leaves your stomach, eating too much at once can trigger nausea. Eating slowly and avoiding fatty foods also helps significantly.
Should I stop my Mounjaro injection if I feel sick?
Never stop your injection without speaking to your prescriber. Mild nausea is a normal side effect that usually improves with time and practical strategies. If nausea is severe or you cannot keep fluids down, contact your GP or prescriber urgently for dose adjustment guidance.
Ready to take control of your weight loss journey?
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