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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Mounjaro Monthly Subscription vs Wegovy: Comparison Guide
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are available as monthly subscriptions through UK private prescribing services, but they differ significantly in cost, mechanism, dosing schedule, and weight loss outcomes. Understanding these differences helps you and your prescriber decide which might be more suitable for your individual situation. Both are prescription-only medicines requiring a clinical assessment before you can start treatment. This guide compares the two side-by-side to help you make an informed decision.
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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 Mounjaro and Wegovy Compare: Key Differences
Mechanism of action: Mounjaro is a dual GIP and GLP-1 receptor agonist, meaning it activates two hormone pathways simultaneously. Wegovy is a GLP-1 receptor agonist only, activating a single pathway. This difference may affect how each medication works in your body, though individual responses vary significantly.
Clinical trial results: In the SURMOUNT-1 trial, Mounjaro at maximum dose (15 mg) produced average weight loss of approximately 20.9% of body weight over 72 weeks. In the STEP-1 trial, Wegovy at maximum dose (2.4 mg) produced average weight loss of approximately 14.9% over 68 weeks. However, these are averages—individual results vary considerably, and both medications work best alongside reduced-calorie diet and increased physical activity.
Dosing: Mounjaro is injected once weekly, starting at 2.5 mg and escalating to a maximum of 15 mg. Wegovy is also once weekly, starting at 0.25 mg and escalating to a maximum of 2.4 mg. Each medication requires a minimum of 4 weeks at each dose level before escalation.
Typical monthly subscription costs: Private UK costs vary by provider and dose, typically ranging from £129–£320 per month for either medication. Exact pricing depends on your current dose level and which private prescribing service you use.
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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.
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Which Medication Might Suit You? Prescriber Assessment
Choosing between Mounjaro and Wegovy is an individual decision made between you and your prescriber based on your medical history, other medications, weight loss goals, and how your body responds to treatment. Both require clinical assessment to confirm you meet eligibility criteria (BMI 30 or above, or BMI 27–29.9 with weight-related health conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease).
If you're eligible for NHS specialist weight management services, your prescriber may have access to one or both medications depending on your regional ICB. If accessing treatment privately, your online prescriber will assess which medication is most appropriate for you. Many people trial one medication and switch to the other if needed, though any change should be managed by your prescriber. Use our free GLP-1 weight loss calculator to estimate potential outcomes at different doses, and track your progress with our progress tracker once you start treatment.
- 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's the main difference between Mounjaro and Wegovy?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist—it activates two hormone pathways. Wegovy (semaglutide) is a GLP-1 agonist only—it activates one pathway. Clinical trials show Mounjaro may produce slightly greater average weight loss, but individual results vary significantly. Both work best with dietary changes and increased physical activity.
Are Mounjaro and Wegovy available on the NHS?
NICE has approved both medications for NHS specialist weight management services, but availability varies significantly by region and waiting lists can be lengthy. Many people access these medications privately through UK online prescribing services, which typically cost £129–£320 per month depending on dose. Ask your GP about NHS options in your area first.
Which medication will help me lose more weight?
Clinical trials suggest Mounjaro may produce slightly higher average weight loss (approximately 20.9% vs 14.9% in primary trials), but this varies greatly between individuals. Some people respond better to one medication than the other. Your prescriber will assess which is more suitable based on your medical history, not on average trial results. Individual outcomes depend on dose, adherence, diet, and lifestyle.
Can I switch from Wegovy to Mounjaro or vice versa?
Yes, but any medication switch must be managed by your prescriber. There is no official established conversion between doses—your prescriber will assess the appropriate starting dose if you switch. Some people find they respond better to one medication than the other after trialling both.
What's included in a monthly subscription for either medication?
A monthly subscription typically includes four weekly injections (the medication in pre-filled pen format), ongoing prescriber support, and access to your prescription through a GPhC-registered pharmacy. Some services include additional support such as dietary advice or progress tracking. Costs and inclusions vary by provider—check directly with your chosen service for details.
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.