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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Mounjaro Going Up In Price — How It Compares to Wegovy
Mounjaro KwikPen costs are rising in the UK private market, prompting many people to compare it with alternative weight loss injections like Wegovy. Both are prescription-only GLP-1-based medications licensed for weight management, but they differ in mechanism, dosing, and cost. This guide explains how Mounjaro and Wegovy compare, what the clinical evidence shows, and how to discuss options with your prescriber. Your choice depends on individual suitability, which is assessed following a clinical consultation.
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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.
Clinical Evidence: SURMOUNT vs STEP Trial Results
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, meaning it activates two natural hormone pathways. In the SURMOUNT-1 clinical trial, participants taking the maximum 15 mg dose lost an average of 20.9% of their body weight over 72 weeks alongside a reduced-calorie diet and increased physical activity.
Wegovy (semaglutide) is a single GLP-1 receptor agonist. In the STEP-1 trial, participants on the maximum 2.4 mg dose lost approximately 14.9% of body weight over 68 weeks under similar lifestyle conditions.
These averages mask individual variation—some people lose more, some less. Both trials involved participants following structured reduced-calorie diets, so weight loss occurred alongside lifestyle change, not medication alone. SURMOUNT data suggests tirzepatide may produce slightly greater average weight loss, though prescriber choice depends on your personal health profile, not trial averages.
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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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Mechanism Difference and Practical Considerations
The key difference is Mounjaro's dual mechanism. By targeting both GIP and GLP-1 pathways, it may provide additional appetite suppression compared to Wegovy's single GLP-1 effect. However, both medications work similarly in practice: they reduce hunger, support feeling fuller sooner, and slow gastric emptying.
Dose and injection frequency: Mounjaro starts at 2.5 mg and escalates to a maximum of 15 mg weekly. Wegovy starts at 0.25 mg and escalates to 2.4 mg weekly. Both are once-weekly injections in a KwikPen device. Side effects are similar—nausea, diarrhoea, and constipation are common during dose titration.
With Mounjaro prices rising, Wegovy may appear more cost-effective initially. However, your prescriber will recommend based on clinical suitability, not cost alone. Use our free GLP-1 weight loss calculator to explore projected outcomes at different doses.
- 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.
Why is Mounjaro going up in price in the UK?
Mounjaro pricing in the private market is set by dispensing pharmacies and reflects supply, demand, and manufacturer pricing. There is no single reason—various factors including import costs, pharmacy margins, and market competition influence KwikPen costs. NHS access through specialist services is not subject to these price fluctuations, though waiting lists remain lengthy in many areas.
Which is cheaper—Mounjaro or Wegovy?
Private pricing varies by pharmacy and dose. At entry-level doses, Wegovy may be cheaper, but this changes at higher doses. Always request an exact quote for your target dose before committing. Prices typically range from £129–£320 per month depending on dose and provider. Cost should not be the only factor—prescriber recommendation based on your health is more important.
Is Mounjaro better than Wegovy?
Not necessarily. Clinical trials suggest tirzepatide (Mounjaro) produced slightly greater average weight loss than semaglutide (Wegovy), but individual results vary widely. "Better" depends on your personal response, side effect tolerance, and health profile. Your prescriber will recommend the most suitable option following a clinical assessment.
Can I switch from Mounjaro to Wegovy if the price rises?
Yes, switching is possible but must be managed by your prescriber. There is no official conversion chart between doses—switching typically involves stopping Mounjaro, waiting an appropriate interval, and starting Wegovy at a low escalation dose. Never switch medications without prescriber guidance.
Does the NHS provide Mounjaro or Wegovy?
Both are available through NHS specialist weight management (tier 3) services in some areas, though availability and waiting times vary significantly by region and integrated care board. Your GP can refer you to your local service. Private prescription is faster but involves medication costs. ```
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