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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Understanding Mounjaro Sickness and How to Access Treatment in the UK
Nausea and sickness are among the most common side effects of Mounjaro (tirzepatide), affecting many people starting this prescription weight management injection. Understanding what to expect, how these side effects typically progress, and how to access Mounjaro in the UK — whether through the NHS or privately — helps you make an informed decision about whether this treatment is right for you. This guide covers everything you need to know about managing sickness on Mounjaro and navigating the UK healthcare system to get it.
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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 Sickness: What to Expect and Managing Side Effects
Nausea is reported by very common — affecting more than 1 in 10 people in clinical trials of Mounjaro. Sickness and vomiting occur in a significant proportion of users, particularly during the dose escalation phase (the first 16 weeks when your dose increases every 4 weeks).
When sickness typically occurs:
- Most common in the first 2–4 weeks of starting Mounjaro or increasing your dose
- Symptoms often improve over time as your body adjusts — typically within 1–2 weeks
- Eating smaller, frequent meals and avoiding fatty or greasy foods may help reduce nausea
- Staying hydrated is important, especially if you experience vomiting
If sickness persists beyond 2 weeks at the same dose, or becomes severe, contact your prescriber immediately. They may recommend staying on your current dose longer before escalating, or adjusting your approach. Your GP or prescriber can also recommend anti-nausea strategies tailored to your situation.
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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.
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Accessing Mounjaro in the UK: NHS vs Private Routes and Costs
NHS access: Mounjaro is available through NHS specialist tier 3 weight management services, approved by NICE. However, access is limited and varies significantly by region. You'll need a GP referral, and waiting times can extend to months or even years in some areas. There is no direct cost to you if prescribed through the NHS.
Private access: Private online prescribing offers faster access without NHS waiting lists. A UK-licensed prescriber conducts an online clinical assessment, and if appropriate, issues a prescription dispensed by a GPhC-registered pharmacy. Costs typically range from £129–£320 per month depending on your dose. Use our GLP-1 weight loss calculator to estimate your potential dose and costs based on your weight and goals.
What to expect during an online consultation: You'll answer detailed health questions about your weight, medical history, medications, and weight-related conditions. The prescriber assesses your eligibility based on BMI (30 or above, or 27+ with weight-related health issues) and whether Mounjaro is safe for you. This process typically takes 24–48 hours. Once approved, your prescription is sent to the dispensing pharmacy, and your Mounjaro KwikPen arrives within 2–5 working days. Always check with your chosen provider about their specific timescales and pricing.
- 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.
Is nausea on Mounjaro permanent?
No. Most people experience nausea predominantly during dose escalation, and symptoms typically improve within 1–2 weeks of starting each new dose. If nausea persists beyond 2 weeks or becomes severe, inform your prescriber — they may adjust your escalation schedule.
Can I access Mounjaro on the NHS in the UK?
Yes, Mounjaro is approved by NICE for NHS specialist weight management services (tier 3). However, availability is limited and regional. You need a GP referral and may face significant waiting times. Private access is faster but involves out-of-pocket costs.
How much does Mounjaro cost privately in the UK?
Private Mounjaro typically costs £129–£320 per month depending on your dose and the prescribing provider. Doses range from 2.5 mg (starting) to 15 mg (maximum). Costs are separate from any online consultation fee, which varies by provider.
What's the difference between Mounjaro and Wegovy for managing sickness?
Both are once-weekly injections for weight management. Mounjaro (tirzepatide) is a dual GIP/GLP-1 agonist; Wegovy (semaglutide) is a GLP-1 agonist only. Nausea rates are comparable. Choice depends on prescriber recommendation, availability, and individual response. Compare using our GLP-1 weight loss calculator.
What should I do if sickness on Mounjaro is unbearable?
Contact your prescriber immediately. Options include staying on your current dose longer, reducing your dose temporarily, switching to a different medication, or stopping treatment. Never adjust your dose yourself. Your prescriber can provide anti-nausea strategies and support tailored to your situation.
Ready to take control of your weight loss journey?
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