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
Free tracker included with every download this week
Switching From Mounjaro To Wegovy In The UK
If you're currently taking Mounjaro (tirzepatide) and considering a switch to Wegovy (semaglutide), you'll want to understand the practical differences between these two GLP-1 medications, how access works in the UK, and what costs are involved. Both are prescription-only weight management injections, but they have different mechanisms, doses, and availability routes. This guide covers the cost and access landscape to help you make an informed decision with your GP or prescriber.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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 Cost And Access Routes For Wegovy
Wegovy costs vary by dose and private provider, typically ranging from approximately £129 to £280 per month depending on which dose you require and which GPhC-registered online pharmacy you choose. Wegovy doses scale from 0.25 mg (starting dose) up to 2.4 mg (maintenance dose), so costs increase as you progress through the dose escalation protocol over 17 weeks. Many private prescribing services require an initial online consultation fee (usually £20–£50), which may be waived if you proceed with a prescription. Unlike the Mounjaro KwikPen format with four pre-loaded doses, Wegovy pens are single-dose devices, meaning you receive one pen per weekly injection. Private access typically involves completing an online health questionnaire, having a video or telephone consultation with a UK-licensed prescriber, and receiving your prescription from a GPhC-registered pharmacy — usually within 24–48 hours. This route bypasses NHS waiting lists entirely, though costs are met privately by the patient.
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 Access Versus Private Routes And The Switch Process
NHS access to Wegovy requires referral to a specialist tier 3 weight management service through your GP, with availability varying significantly across different regions and integrated care boards. Waiting lists can extend several months or longer in some areas. If you're currently on Mounjaro through an NHS specialist service and wish to switch to Wegovy, this decision must be managed by your specialist prescriber — there is no official conversion dose chart, though approximate equivalences exist (for example, Mounjaro 5 mg is roughly equivalent to Wegovy 0.5 mg). Your prescriber will assess whether the switch is clinically appropriate based on your response to Mounjaro, any side effects you've experienced, and your treatment goals. Any switch between medications requires a period off treatment and a restart on the new medication's dose escalation protocol. Using our GLP-1 weight loss calculator can help you understand projected outcomes at different doses of either medication, while our BMI calculator provides context for your current health metrics.
- 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 Wegovy cheaper than Mounjaro in the UK?
Private costs are similar — both typically range from £129–£280 per month depending on dose. Wegovy pens are single-dose devices, while Mounjaro KwikPens contain four weeks of doses, which may affect perceived value. NHS costs are zero if eligible, but waiting times can be long. Direct comparison depends on your specific dose and chosen provider.
Can I switch from Mounjaro to Wegovy on the NHS?
Possible, but requires your specialist prescriber's assessment and approval. NHS switching depends on your response to Mounjaro, side effects experienced, and clinical judgment. This cannot be done independently — your GP or specialist must manage the switch. Regional availability of Wegovy through NHS services also varies.
What's the difference between Mounjaro and Wegovy?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, while Wegovy (semaglutide) is a GLP-1-only medication. Mounjaro typically achieves slightly higher average weight loss (~20.9% vs ~14.9%) in clinical trials. Both require weekly injections; Mounjaro dosing goes up to 15 mg, Wegovy up to 2.4 mg. Individual results vary significantly.
How long does the online consultation take for private Wegovy?
Most online consultations take 15–30 minutes. You'll complete a detailed health questionnaire beforehand, then have a video or telephone appointment with a UK-licensed prescriber. If approved, your prescription is sent to a GPhC-registered pharmacy, typically dispensed within 24–48 hours.
Will my GP help me switch from Mounjaro to Wegovy?
Your GP can facilitate referral to a specialist service for NHS switching, or provide general support if you're accessing Wegovy privately. However, the clinical decision to switch medications must be made by your current prescriber (likely a specialist) or a new prescriber doing a fresh assessment. Your GP cannot prescribe these medications in primary care.
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.