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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Which Is Best: Wegovy or Mounjaro? UK Cost & Access
Deciding between Wegovy and Mounjaro in the UK depends on cost, access, medical eligibility, and how your body responds to treatment. Both are prescription-only GLP-1 weight loss injections licensed in the UK — Mounjaro (tirzepatide) uses a dual mechanism, whilst Wegovy (semaglutide) uses a single GLP-1 pathway. This guide compares both options to help you understand the practical differences in accessing them privately or through the NHS, including pricing and how to get started.
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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.
UK Private Prescription Costs & Monthly Pricing
Both Wegovy and Mounjaro are available through private prescription in the UK following an online clinical assessment. Costs vary significantly depending on your starting dose and the provider you choose.
- Wegovy (semaglutide): typically £129–£299 per month depending on dose, with the starting dose (0.25 mg) usually at the lower end and the maximum dose (2.4 mg) at the higher end
- Mounjaro (tirzepatide): typically £149–£320 per month depending on dose, with dose titration starting at 2.5 mg and escalating to 15 mg over several months
Private online prescribers conduct a clinical assessment (usually via video or questionnaire) to confirm you meet eligibility criteria: BMI 30 or above, or BMI 27–29.9 with weight-related health conditions. Treatment is then dispensed by a GPhC-registered pharmacy. Costs are usually per dose or per month, not per injection — most providers supply a four-week dose pack.
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.
NHS vs Private Routes & How to Access Each
The NHS route requires referral to a specialist tier 3 weight management service through your GP. NICE has approved both tirzepatide (Mounjaro) and semaglutide (Wegovy) for NHS use, but availability varies significantly by region and waiting times can be months or even years. NHS prescription is free once approved, but you cannot choose the medication — your specialist service decides which is appropriate for your health profile.
The private route is faster: book an online consultation with a UK-licensed prescriber, complete a health assessment, and if approved, your prescription is sent to a GPhC-registered pharmacy. You can typically start treatment within 2–5 days. Use our free BMI calculator above to check your starting point, and our GLP-1 weight loss calculator to compare projected weight loss outcomes with each medication.
- 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 or Wegovy more expensive in the UK?
Costs are similar — typically £129–£320 per month privately depending on dose. Wegovy starting doses cost less; Mounjaro maximum doses may cost slightly more. Ask your prescriber for their specific pricing. NHS prescription is free if approved, but depends on your region.
Can I get Wegovy or Mounjaro on the NHS?
Yes, both are NICE-approved for NHS use. You need referral from your GP to a specialist tier 3 weight management service. Availability and waiting times vary by region — some areas have 12+ month waits. Private prescription is typically faster (2–5 days) but requires self-funding.
How does dose titration affect cost?
Both medications start at a low dose and increase gradually over weeks. Mounjaro dose titration ranges from 2.5 mg to 15 mg; Wegovy from 0.25 mg to 2.4 mg. Most private prescribers charge per dose escalation, so costs build up as you move through the titration schedule over 4–5 months.
What's the difference between Mounjaro KwikPen and Wegovy pens?
Mounjaro comes as a pre-filled KwikPen with 4 doses (4-week supply) per box. Wegovy comes as pre-filled auto-injection pens. Both are once-weekly injections. Storage and disposal are similar — keep refrigerated until first use, then 30 days at room temperature.
Which medication will work better for me — Mounjaro or Wegovy?
Results vary individually. Clinical trials show Mounjaro (tirzepatide) may achieve slightly higher average weight loss (~21% body weight) than Wegovy (~15%), but both work well for many people. Only a prescriber can assess which is appropriate based on your medical history, current medications, and health conditions.
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.