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
Is Wegovy 0.5mg Equivalent to Mounjaro?
Wegovy 0.5mg is not directly equivalent to Mounjaro — they are different medications with different mechanisms. Wegovy (semaglutide) is a GLP-1 receptor agonist, whilst Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist. However, in clinical practice, Wegovy 0.5mg is sometimes considered roughly equivalent to Mounjaro 5mg in terms of weight loss potential, though individual responses vary. This guide explains the dosing, NHS availability, and how to choose between them 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.
NHS Eligibility and Dose Titration in the UK
Both Wegovy and Mounjaro are prescription-only medicines available in the UK for adults with a BMI of 30 or above, or 27–29.9 with weight-related health conditions such as type 2 diabetes, hypertension, or sleep apnoea. Wegovy starts at 0.25mg and titrates up to 2.4mg over 16 weeks, whilst Mounjaro begins at 2.5mg and escalates to 15mg over 20 weeks. The STEP clinical trials showed Wegovy 2.4mg achieves approximately clinically studied weight loss on average, whilst the SURMOUNT trial demonstrated Mounjaro 15mg achieves up to clinically studied weight loss. NHS access is through specialist tier 3 weight management services, with significant regional variation in availability and waiting times across UK ICBs.
- Wegovy doses: 0.25mg → 0.5mg → 1mg → 1.7mg → 2.4mg (once weekly)
- Mounjaro doses: 2.5mg → 5mg → 7.5mg → 10mg → 12.5mg → 15mg (once weekly)
- Both require a clinical assessment before prescription
- Individual weight loss varies based on diet, activity, and genetic factors
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 vs Private Prescribing in the UK
NHS route: Referral to a tier 3 specialist weight management service from your GP. This may involve a waiting list of several months in many areas. Not all NHS regions currently commission these services equally. Private route: Online consultation with a UK-licensed prescriber, prescription issued if appropriate, dispensed by a GPhC-registered pharmacy. No NHS referral required, available within days. Use our GLP-1 weight loss calculator to estimate potential results at different doses, and our BMI calculator to assess your starting eligibility. Costs range from approximately £129–£320 monthly depending on dose and provider. Both routes require ongoing clinical review and lifestyle changes including reduced-calorie diet and increased physical activity for optimal 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 Wegovy 0.5mg the same strength as Mounjaro 5mg?
Not exactly. Whilst Wegovy 0.5mg and Mounjaro 5mg are sometimes considered roughly equivalent in clinical practice, they work differently. Mounjaro activates both GIP and GLP-1 pathways, whilst Wegovy activates GLP-1 only. This dual mechanism may explain why Mounjaro shows slightly higher average weight loss in trials. Direct equivalence has not been formally established by MHRA. Any switch between medications should be managed by a prescriber.
How long does it take to reach Wegovy 0.5mg on the NHS?
Wegovy starts at 0.25mg for weeks 1–4, then increases to 0.5mg for weeks 5–8. If prescribed through NHS tier 3 services, the entire titration schedule takes 16 weeks to reach maximum dose (2.4mg). However, waiting times for NHS referral and initial appointment can vary from weeks to months depending on your regional ICB and current service capacity.
Can I switch from Wegovy to Mounjaro on the NHS?
Yes, a switch is possible but requires prescriber approval. Your tier 3 weight management service or GP would need to arrange this. There is no official NHS conversion chart — the switch would typically follow normal dose titration protocols starting with a low dose of Mounjaro. Any medication change requires clinical reassessment and ongoing monitoring.
What is the main difference between Wegovy and Mounjaro?
Wegovy (semaglutide) is a single GLP-1 receptor agonist. Mounjaro (tirzepatide) activates both GIP and GLP-1 pathways. Clinical trials suggest Mounjaro may produce slightly higher average weight loss (~21% vs ~15%), though individual results vary widely. Both are once-weekly injections, prescription-only, and require NHS referral or private assessment in the UK.
Which is cheaper — Wegovy or Mounjaro on the NHS?
Both are available on the NHS at no cost to patients if prescribed through tier 3 specialist services. Private costs vary by dose and provider, typically £129–£320 monthly for either medication. NHS availability depends on your region's ICB commissioning decisions and current waiting list status. Ask your GP about NHS routes or explore private options if NHS waiting times are long in your area.
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.