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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Feeling Sick on Mounjaro — Managing Nausea and Understanding UK Costs
Nausea is one of the most common side effects when starting Mounjaro (tirzepatide), particularly during dose titration. If you're experiencing sickness on Mounjaro, this is a normal response to the medication — but there are practical strategies to manage it. This guide explains why nausea happens, how to cope with it, and what Mounjaro costs across the NHS and private routes in the UK, so you can make informed decisions about access and affordability.
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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 How to Manage It
Nausea affects more than 1 in 10 people taking Mounjaro, especially in the first 4–8 weeks and during dose titration (when your dose increases weekly). Mounjaro works by activating GLP-1 and GIP hormone pathways in the gut, which slow how quickly food leaves your stomach and signal fullness to your brain — these mechanisms can trigger temporary queasiness.
- Start with small, frequent meals instead of large ones
- Avoid fatty, greasy, or heavily spiced foods — stick to bland, protein-rich options
- Stay hydrated with water, herbal tea, or clear broths
- Eat slowly and chew thoroughly
- Take anti-nausea medication if prescribed by your healthcare provider
- Most people find nausea improves significantly after 2–4 weeks at each dose level
If nausea is severe or persists beyond 4 weeks, contact your prescriber — they may suggest staying at your current dose longer before increasing, or trying alternative management strategies.
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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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Mounjaro Cost and Access in the UK
NHS access: Mounjaro is available through NHS specialist weight management services (tier 3) for eligible adults. Access is free at point of use but availability varies significantly by region and waiting lists can extend several months. Your GP can refer you to your local NHS service.
Private access: Private prescription and dispensing typically costs £129–£320 per month depending on your dose. A KwikPen (containing 4 weekly doses) ranges from £130–£280. You'll need an online consultation with a UK-licensed prescriber (usually £20–£50) before a prescription is issued by a GPhC-registered pharmacy. Private access is faster than NHS routes and doesn't require a GP referral.
- 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 mean Mounjaro isn't working?
No. Nausea is a common side effect that typically improves within 2–4 weeks, and it doesn't indicate treatment failure. Clinical trials show weight loss benefits occur even when people experience nausea early on. Your prescriber can help manage symptoms while you continue treatment.
Should I stop Mounjaro if I feel sick?
Don't stop without consulting your prescriber. If nausea is mild to moderate, dietary adjustments and time often help. If it's severe or affecting your ability to eat and stay hydrated, contact your healthcare provider — they may slow your dose progression or recommend medication to manage nausea.
Is Mounjaro cheaper on the NHS or privately in the UK?
NHS prescriptions are free at point of use, but access requires a referral and can involve long waiting lists. Private prescriptions typically cost £130–£280 per KwikPen depending on dose. If quick access matters to you, private may be preferable; if cost is the priority, NHS is free but slower.
What's included in the private consultation fee for Mounjaro?
Private online consultations (typically £20–£50) include an assessment of your health history, BMI, weight-related conditions, and suitability for tirzepatide. If approved, a UK-licensed prescriber issues a prescription, which a GPhC pharmacy then dispenses. Consultation fees are often separate from medication costs.
How long does nausea last when starting Mounjaro?
Most people find nausea peaks in week 1–2 of each new dose and significantly improves by week 3–4. Some experience mild queasiness throughout treatment, but severity typically decreases over time. If nausea persists beyond 4 weeks, discuss this with your prescriber.
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.