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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Switching from Mounjaro to Wegovy in the UK
If you're considering switching from Mounjaro (tirzepatide) to Wegovy (semaglutide) in the UK, you'll want to understand the costs, access routes, and what the switch actually involves. Both are prescription-only weight management injections, but they work differently and have different access pathways. This guide explains your options, whether you're on the NHS or using private prescription services, and what to expect during the transition.
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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.
UK Private Prescription Costs for Wegovy
Wegovy costs vary significantly depending on the dose and the private prescribing service you use. Typical UK private prescription costs range from £130 to £300 per month, though this varies by provider and dose level. A standard starter pack (0.25 mg to 0.5 mg doses) usually costs £130–£180 per month, while maintenance doses (1 mg to 2.4 mg) cost £220–£300 monthly. These prices include the prescription assessment, the medication itself, and four weeks' supply. Some providers offer subscription models with slight discounts if you commit to ongoing treatment. Unlike the NHS, which has limited availability and long waiting lists, private routes offer faster access — typically prescription issued within 24–48 hours of a successful online clinical assessment. However, you must meet eligibility criteria: a BMI of 30 or above, or 27+ with weight-related health conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease. Costs are not covered by the NHS when obtained privately, so you'll pay the full amount out of pocket each month.
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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.
NHS vs Private Access: Which Route is Right for You?
The NHS route is free at the point of use but involves waiting to see your GP, a referral to a tier 3 specialist weight management service, and then a waiting list — which can be 6 months to 2+ years depending on your region. The NHS has strict protocols around eligibility and a more thorough assessment process. The private route is faster: you complete an online consultation with a UK-licensed prescriber, and if approved, your prescription is issued within days. You then collect your Mounjaro KwikPen or Wegovy auto-injection from a GPhC-registered pharmacy. Private prescribing doesn't require a GP referral. When switching from Mounjaro to Wegovy, your prescriber will consider your current Mounjaro dose and recommend an appropriate Wegovy starting point — though these are not directly equivalent. Mounjaro's maximum is 15 mg weekly, while Wegovy's is 2.4 mg weekly; Mounjaro is a dual GIP and GLP-1 agonist, whereas Wegovy is GLP-1 only. Use our free GLP-1 weight loss calculator to help compare projected outcomes at different doses, and our BMI calculator to confirm your eligibility before pursuing either route.
- 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.
How much does Wegovy cost per month in the UK privately?
Private prescription costs for Wegovy typically range from £130 to £300 per month depending on the dose. Starter doses (0.25–0.5 mg) cost around £130–£180, while maintenance doses (1–2.4 mg) cost £220–£300. Prices vary between private prescribing services. Always check what's included: prescription fee, medication, and delivery.
Can I switch from Mounjaro to Wegovy on the NHS?
NHS switching between weight loss medications is possible but rare and varies significantly by region. Most NHS specialists manage one medication at a time. If you want to switch, discuss it with your GP or specialist service — they'll assess whether it's clinically appropriate. Waiting times apply either way.
Is there an exact Mounjaro to Wegovy dose conversion?
There is no official established conversion chart, but approximate equivalences exist: Mounjaro 5 mg ≈ Wegovy 0.5 mg, Mounjaro 10 mg ≈ Wegovy 1.7 mg, Mounjaro 15 mg ≈ Wegovy 2.4 mg. However, any switch must be managed by your prescriber — they'll assess your health and recommend the appropriate starting dose for Wegovy.
How long does it take to get Wegovy through a private UK prescription?
Private prescribing is fast. After completing an online consultation (typically 15–30 minutes), a UK-licensed prescriber reviews your application. If approved, your prescription is usually issued within 24–48 hours. Your pharmacy then dispatches the medication, arriving within 2–5 working days depending on delivery.
Do I need a GP referral to get Wegovy privately in the UK?
No. Private weight loss prescriptions don't require a GP referral. You can contact a private prescribing service directly, complete an online clinical assessment with a UK-licensed prescriber, and receive a prescription if eligible. However, informing your GP is advisable for safety reasons, especially if you're on other medications.
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.