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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Wegovy 1mg vs Mounjaro — UK NHS Context
Both Wegovy and Mounjaro are prescription-only weight management injections licensed in the UK, but they work differently and have different dosing schedules. Wegovy (semaglutide) is a GLP-1 receptor agonist, while Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist — meaning it activates two hormone pathways instead of one. Understanding the differences is important if you're considering weight loss medication through the NHS or privately. This guide explains how they compare in terms of mechanism, doses, clinical evidence, and UK access routes.
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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.
How Wegovy and Mounjaro Compare — Mechanism and Doses
Wegovy (semaglutide) starts at 0.25 mg once weekly and escalates over 16 weeks to a maximum of 2.4 mg. In STEP clinical trials, patients taking 2.4 mg Wegovy lost an average of approximately 14.9% of their body weight over 68 weeks alongside a reduced-calorie diet and increased physical activity.
Mounjaro (tirzepatide) starts at 2.5 mg once weekly and escalates over at least 20 weeks to a maximum of 15 mg. In SURMOUNT trials, patients at the 15 mg dose lost an average of approximately 20.9% of body weight — though at 10 mg (mid-range) the average was around 19.5%.
- Wegovy: single GLP-1 mechanism, progresses from 0.25 mg to 2.4 mg
- Mounjaro: dual GIP+GLP-1 mechanism, starts higher at 2.5 mg and goes up to 15 mg
- Both require once-weekly injections and a reduced-calorie diet for best results
- Individual results vary significantly — averages do not predict personal outcomes
The dual mechanism in Mounjaro may provide additional appetite regulation, which is why some patients experience greater weight loss. However, clinical response is highly individual.
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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 Eligibility and UK Access Routes
In the UK, both Wegovy and Mounjaro are available through NHS specialist weight management services (tier 3) or privately through a UK-licensed prescriber. NHS access requires referral from your GP to a specialist weight management service, but availability varies significantly by region and waiting lists can be lengthy.
To qualify for either medication on the NHS, you typically need a BMI of 30 kg/m² or above, or 27–29.9 with weight-related health conditions such as type 2 diabetes, hypertension, or sleep apnoea. Adults of South Asian, Chinese, Black African, or Black Caribbean heritage may be eligible at lower BMI thresholds (from 27.5 kg/m²) due to higher cardiovascular risk at lower weights.
- NHS route: GP referral to tier 3 service, longer wait, no cost at point of delivery
- Private route: online consultation with UK-licensed prescriber, faster access, individual cost varies
- Both require clinical assessment before prescription — neither is available over-the-counter
Check your BMI using our free BMI calculator above to see whether you might meet initial eligibility criteria. Our GLP-1 weight loss calculator can also help you understand potential weight loss outcomes at different doses of either medication, based on clinical trial averages. When considering which medication is right for you, a GP or specialist prescriber can assess your individual health profile and recommend the most suitable option.
- 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.
What is the main difference between Wegovy and Mounjaro?
Wegovy (semaglutide) is a GLP-1 receptor agonist that works on one hormone pathway. Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist, activating two pathways. This dual mechanism in Mounjaro may lead to slightly greater average weight loss, but individual responses vary.
Can I get Wegovy or Mounjaro on the NHS in the UK?
Yes, both are available through NHS specialist tier 3 weight management services if you meet eligibility criteria (BMI 30 or above, or 27–29.9 with weight-related health conditions). You'll need a GP referral. Private access is available faster through online UK-licensed prescribers without NHS referral.
How much weight loss can I expect from Wegovy 1mg?
Wegovy is not typically used as a maintenance dose — 1 mg is an escalation step. At maintenance (2.4 mg), clinical trials showed average weight loss of approximately 14.9% of body weight over 68 weeks alongside diet and exercise. Results vary significantly between individuals.
Which medication has fewer side effects — Wegovy or Mounjaro?
Both have similar common side effects (nausea, diarrhoea, constipation, stomach pain). Rates are comparable in clinical trials. Individual tolerability varies. If you experience side effects on one, switching may help, but this requires prescriber guidance.
How do I know if I'm eligible for weight loss medication in the UK?
Use our free BMI calculator above to check your BMI. If it's 30 or above (or 27+ with health conditions), ask your GP about referral to NHS tier 3 services or consider a private online consultation with a UK-licensed prescriber for faster access.
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.