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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Has Anyone Switched From Mounjaro to Wegovy in the UK?
Yes, some UK adults do switch between Mounjaro (tirzepatide) and Wegovy (semaglutide) for weight management. This might happen for various reasons — side effects, cost, personal preference, or clinical guidance. Both are prescription-only GLP-1 and GLP-1 receptor agonist medications licensed in the UK for weight loss. Understanding the differences in cost and how to access each one can help you make an informed decision with your prescriber. This guide covers the practical reality of switching and what's involved 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.
Wegovy Cost and Private Access in the UK
Wegovy (semaglutide 2.4 mg) is available privately through UK-licensed online prescribers and GPhC-registered pharmacies. Typical private costs range from £129 to £320 per month, depending on the dose and provider. Starting doses (0.25 mg and 0.5 mg) are usually cheaper than maintenance doses (1.7 mg and 2.4 mg). Unlike Mounjaro, Wegovy requires a daily injection rather than once-weekly, which some people find less convenient. Private online consultations typically cost £40–£80 and take 10–20 minutes. You'll be asked about your medical history, current medications, and weight-related health conditions. If approved, your prescription is sent directly to a pharmacy, which dispatches within 1–2 working days. Storage requires refrigeration (2–8°C) until first use, then room temperature for up to 30 days after opening.
- Private Wegovy costs typically £129–£320/month depending on dose
- Online consultations with UK prescribers cost £40–£80
- Daily injection (not weekly like Mounjaro)
- Available without NHS referral through private prescribing routes
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 Access and Switching Between Medications
On the NHS, both Mounjaro and Wegovy are available through specialist tier 3/4 weight management services, but access is highly variable by region and often involves lengthy waiting lists. Switching between them on the NHS requires discussion with your specialist team — they may consider dose equivalence, side effect profile, or clinical suitability. Privately, you can switch more flexibly — some people begin with one medication and request a different one at their next online consultation if they're experiencing side effects or prefer a different dosing schedule. A prescriber will assess whether switching is appropriate based on your health. You cannot be prescribed both simultaneously. If switching, allow 1–2 weeks between stopping one and starting another, unless otherwise advised by your prescriber. Our free GLP-1 weight loss calculator can help you understand potential outcomes from either medication before discussing with your prescriber.
- 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.
Can you switch from Mounjaro to Wegovy on the NHS?
Yes, but you'll need to discuss this with your NHS specialist weight management team. Switching requires clinical assessment and there may be waiting time involved. NHS access varies significantly by region, and some areas have longer waiting lists than others.
Is Wegovy cheaper than Mounjaro in the UK?
Costs vary by provider and dose, but both typically range £129–£320/month privately. Mounjaro uses once-weekly injections; Wegovy requires daily injections. Overall costs depend on your chosen dose and supplier rather than which medication you pick.
How long does it take to switch from Mounjaro to Wegovy privately?
You can usually switch at your next online consultation (typically every 4–12 weeks). Once approved, your new prescription is dispensed within 1–2 working days. Some prescribers recommend a 1–2 week gap between stopping one and starting another.
Do you need a new prescription for both Mounjaro and Wegovy?
Yes, each medication requires its own separate prescription. You cannot use both at the same time. If switching, your previous prescription will be stopped before a new one is issued.
What's the main difference between Mounjaro and Wegovy for weight loss?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist with once-weekly dosing; Wegovy (semaglutide) is a GLP-1-only agonist with daily dosing. Clinical trials showed both support weight loss, though individual results vary. Mounjaro may offer slightly stronger effects for some people, but Wegovy has more established long-term data.
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.