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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Cheapest 2.5 Mounjaro UK — Cost and Comparison Guide
Mounjaro 2.5 mg is the starting dose for tirzepatide weight management in the UK, and cost varies significantly depending on whether you access it through the NHS or privately. While NHS access through specialist weight management services is free, private prescriptions typically cost £130–£180 per month for the 2.5 mg dose. This introductory dose is only used for the first four weeks before stepping up to higher doses. Understanding both cost and how Mounjaro compares to alternatives like Wegovy can help you make an informed decision about prescription weight loss options in the UK.
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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.
Mounjaro 2.5 mg vs Wegovy — Trial Data and Mechanisms
Mounjaro (tirzepatide) and Wegovy (semaglutide) are both GLP-1 weight loss medications available in the UK, but they work differently. Mounjaro is a dual GIP and GLP-1 receptor agonist, meaning it activates two hormone pathways that regulate appetite and blood sugar. Wegovy is a GLP-1-only agonist, activating a single pathway.
Clinical trial data shows these differences may impact weight loss outcomes:
- Mounjaro (SURMOUNT-1): Participants on the 5 mg maintenance dose lost approximately 15% body weight on average; those on 15 mg lost around 20.9% after 72 weeks
- Wegovy (STEP-1): Participants lost approximately 14.9% body weight on average at the maximum 2.4 mg dose after 68 weeks
Both medications are used alongside diet and increased physical activity. Your GLP-1 weight loss calculator can help you estimate potential weight loss at different doses, though individual results vary significantly based on adherence, lifestyle changes, and personal metabolism.
Clinically BackedWeight Loss
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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.
Free Weight Loss Tools & Guides
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
Cost, Accessibility, and Which Suits You
NHS access: Free through tier 3 specialist weight management services, but availability varies by region and waiting lists can be lengthy. NICE approval means both Mounjaro and Wegovy are supported by NHS guidelines for eligible adults.
Private costs: The 2.5 mg starting dose typically costs £130–£180 monthly from private UK prescribers. Mounjaro's dual mechanism may suit some individuals better than Wegovy, but this is assessed during clinical consultation. Neither medication is suitable if you're pregnant, breastfeeding, or under 18. Your prescriber will assess your BMI, health conditions, and suitability before prescribing. Both require commitment to lifestyle changes for best results.
- 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 Mounjaro 2.5 mg the only starting dose in the UK?
Yes, Mounjaro 2.5 mg is the mandatory starting dose in the UK. You remain on this dose for the first four weeks before your prescriber considers escalating to 5 mg. This slow titration reduces side effects like nausea and allows your body to adapt to the medication.
Why is Mounjaro more expensive than Wegovy in some UK pharmacies?
Cost varies between private prescribers and pharmacies. Mounjaro's dual mechanism (GIP + GLP-1) versus Wegovy's single GLP-1 mechanism doesn't directly affect price, but supply, demand, and individual pharmacy margins do. Always compare quotes from multiple GPhC-registered online pharmacies.
Can I access Mounjaro 2.5 mg free on the NHS?
Yes, if your GP refers you to a tier 3 specialist weight management service and you meet eligibility criteria (BMI ≥30, or BMI 27–29.9 with weight-related health conditions). However, NHS availability varies significantly by region, and waiting times can be several months.
How long do I stay on the 2.5 mg dose before increasing?
Mounjaro guidance recommends staying on 2.5 mg for at least four weeks before your prescriber considers escalating to 5 mg. If you experience tolerability issues, you may remain on 2.5 mg longer or discontinue under medical guidance.
Which is cheaper long-term — Mounjaro or Wegovy?
Long-term cost comparison depends on your maintenance dose. Mounjaro's maximum is 15 mg weekly; Wegovy's is 2.4 mg weekly. At equivalent price-per-dose, costs are similar, but many patients on Mounjaro achieve results at lower doses. Private costs typically range £130–£320 monthly depending on final dose and provider.
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.