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
Does Mounjaro Make You Feel Sick?
Yes, nausea is a very common side effect of Mounjaro (tirzepatide), affecting more than 1 in 10 people. However, most people find nausea improves significantly after the first few weeks as their body adjusts to the medication. Nausea is most pronounced when you first start Mounjaro or increase your dose, and tends to settle once you've been on a stable dose for several weeks. This guide covers what to expect, how to manage it, and how to access Mounjaro in the UK through NHS specialist services or private prescription.
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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 Common Is Nausea with Mounjaro?
Nausea is the most frequently reported side effect of Mounjaro. Clinical trial data shows that nausea affects approximately 25–40% of people taking the medication, making it very common but not universal. Most people experience mild to moderate nausea rather than severe nausea that causes vomiting.
Nausea typically appears within the first few days of starting Mounjaro or after a dose increase, and usually improves within 1–2 weeks as your body adapts. The severity often peaks when you first inject and gradually lessens over time. Other common gastrointestinal side effects include diarrhoea, constipation, and stomach discomfort, but these also tend to improve with continued use at a stable dose.
- Nausea is most common at the 5 mg and 10 mg dose stages
- Eating smaller, lighter meals can help reduce nausea
- Staying hydrated is important, especially if you experience vomiting
- Anti-nausea medication (such as ginger or over-the-counter remedies) may help while your body adjusts
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.
Mounjaro Cost and Access in the UK
Access to Mounjaro in the UK varies significantly between NHS and private routes. Through the NHS, Mounjaro is available via specialist tier 3 weight management services, though waiting lists are often lengthy and vary by region. Your GP can refer you if you meet eligibility criteria: a BMI of 30 or above, or 27–29.9 with weight-related health conditions such as type 2 diabetes or high blood pressure.
Privately, Mounjaro is available through GPhC-registered online prescribing services following a clinical consultation. Private costs typically range from £150–£280 per month depending on your dose. The KwikPen device contains four weekly doses, so costs reflect your current dose titration stage. Both routes require a prescription from a UK-licensed prescriber who will assess your suitability and provide ongoing support.
- 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 from Mounjaro last?
Most people experience nausea for 1–2 weeks after starting or increasing their dose. Nausea typically improves significantly once your body adjusts to the medication. If nausea persists beyond 3–4 weeks or is severe, contact your prescriber — they may adjust your dose or provide additional support.
What's the difference between Mounjaro and Wegovy for nausea?
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) cause nausea similarly, though Mounjaro's dual GIP/GLP-1 mechanism may cause slightly different gastrointestinal effects in some people. Individual responses vary. Your prescriber can discuss which medication might suit you better based on your health profile.
Can I take anti-nausea medication with Mounjaro?
Yes, over-the-counter anti-nausea remedies such as ginger supplements or travel sickness bands may help. However, always inform your prescriber about any medications or supplements you're taking, as some may interact with Mounjaro or affect how well it works.
How do I access Mounjaro on the NHS in the UK?
Ask your GP for a referral to your local NHS tier 3 specialist weight management service. You must meet eligibility criteria: BMI 30+ or 27–29.9 with weight-related health conditions. NHS availability varies by region, and waiting times can be several months. Check your local integrated care board (ICB) for current waiting lists.
What's the average cost of Mounjaro on prescription privately?
Private prescription costs typically range from £150–£280 per month depending on your current dose. Mounjaro KwikPens contain four weekly doses, so monthly cost depends on your dose stage (2.5 mg through to 15 mg). Prices vary between providers, so it's worth comparing. Use our free GLP-1 weight loss calculator to estimate potential results at different doses.
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.