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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Nausea and Sickness on Mounjaro — How to Manage It
Feeling sick or nauseous is one of the most common side effects of Mounjaro (tirzepatide), especially when you first start the medication or increase your dose. Nausea affects many people taking this GLP-1 and GIP receptor agonist, but it often improves over time as your body adjusts. Understanding why this happens, how to manage it, and your options for accessing Mounjaro in the UK can help you make an informed decision about whether this prescription-only weight management injection is right for you.
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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.
Why Mounjaro Causes Nausea and Managing Side Effects
Mounjaro works by activating GLP-1 and GIP hormone pathways, which signal to your brain that you are full and slow how quickly food leaves your stomach. This mechanism, whilst effective for weight management, can trigger nausea — especially in the first few weeks or when your dose increases. Clinical trials showed nausea was very common, affecting more than 1 in 10 people.
Managing nausea effectively:
- Eat small, frequent meals rather than large portions — your stomach empties more slowly on Mounjaro
- Avoid fatty or greasy foods, which can worsen nausea
- Stay hydrated by sipping water throughout the day
- Take your injection at a consistent time each week
- Take anti-nausea medication (such as metoclopramide) if prescribed by your GP — discuss this before starting Mounjaro
- Most people find nausea improves after 4–8 weeks as their body adapts to the dose
If nausea is severe or persistent, contact your prescriber — dose adjustment or alternative management strategies may help.
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.
Accessing Mounjaro in the UK — NHS Routes and Private Cost
NHS access: Mounjaro is approved by NICE for NHS use, but availability is limited to specialist tier 3 and tier 4 weight management services. Your GP can refer you, but waiting lists vary significantly by region (ICB). Once approved, Mounjaro is free on the NHS — though access may require attending specialist clinics.
Private access: You can obtain Mounjaro privately through UK-registered online prescribing services. After an online consultation with a licensed prescriber, a prescription is issued if clinically appropriate. Cost ranges from approximately £129–£280 per month depending on your dose, with the KwikPen supplied by a GPhC-registered pharmacy. Private treatment starts immediately — no NHS waiting list.
Use our free GLP-1 weight loss calculator to estimate potential results at different Mounjaro doses before committing to 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.
Will the nausea from Mounjaro go away?
Yes, in most people. Nausea is very common when starting or increasing doses, but typically improves within 4–8 weeks as your body adjusts. If it persists or is severe, contact your prescriber — they may suggest dose adjustment, anti-nausea medication, or dietary changes to help manage it.
How much does Mounjaro cost privately in the UK?
Private Mounjaro costs approximately £129–£280 per month depending on your dose and provider. Starting doses (2.5 mg) are cheaper; higher maintenance doses (10–15 mg) cost more. Prices vary between online prescribing services, so it's worth comparing. NHS provision is free but access is limited and involves waiting lists.
Can I get Mounjaro on the NHS in the UK?
Yes, NICE has approved tirzepatide (Mounjaro) for use within NHS specialist weight management services. However, you must be referred by your GP to a tier 3 or tier 4 service, and availability varies significantly by region. Waiting lists can be several months to over a year in some areas. Private access avoids NHS waiting lists.
What's the difference between Mounjaro and Wegovy for nausea?
Both Mounjaro and Wegovy are GLP-1 (or GLP-1/GIP) medications and both commonly cause nausea. Mounjaro has a dual mechanism (GIP + GLP-1), whilst Wegovy is GLP-1-only. Clinical trials suggest both cause similar rates of nausea. Individual response varies, so your prescriber can advise which might suit you better based on your health profile.
How do I get a private prescription for Mounjaro in the UK?
Register with a UK online prescribing service (GPhC-registered), complete an online health questionnaire and consultation, and a licensed UK prescriber assesses whether Mounjaro is suitable. If approved, a prescription is issued and dispensed by a regulated pharmacy. The process typically takes 24–48 hours from consultation to receiving your KwikPen.
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.