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 vs Wegovy: Next Day Delivery Comparison
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are available for next day delivery through UK prescription services, but they work differently and produce different weight loss results. This guide compares the two medications side by side—their mechanisms, clinical trial data, doses, side effects, and how to access them. Both are prescription-only and require a clinical assessment before being prescribed.
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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 Work Differently
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, meaning it activates two natural hormone pathways. This dual mechanism may help regulate appetite more effectively than single-pathway medications. In the SURMOUNT clinical trials, Mounjaro helped participants lose an average of 15–21% of their body weight at the maximum 15 mg dose over 72 weeks, alongside a reduced-calorie diet and increased physical activity.
Wegovy (semaglutide) is a GLP-1 receptor agonist only, activating a single hormone pathway. In the STEP clinical trials, Wegovy helped participants lose an average of approximately 15% of body weight at the 2.4 mg dose over 68 weeks, also alongside lifestyle changes. Both medications slow gastric emptying and support feeling fuller after meals, but Mounjaro's dual action may produce slightly greater average weight loss—though individual results vary significantly.
- Mounjaro: starts at 2.5 mg, escalates to maximum 15 mg weekly
- Wegovy: starts at 0.25 mg, escalates to maximum 2.4 mg weekly
- Both: once-weekly injections available through UK prescribing services
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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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Eligibility, Access, and Individual Suitability
Both medications are prescription-only in the UK and require a clinical assessment to determine suitability. Eligibility criteria are identical: adults with a BMI of 30 kg/m² or above, or 27–29.9 kg/m² with weight-related health conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease. For people of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds (27.5+) may apply. Use our free GLP-1 weight loss calculator to explore potential outcomes at different doses, and our BMI calculator to check whether you might meet eligibility criteria. A prescriber will assess your individual health profile and recommend the most suitable option—Mounjaro, Wegovy, or another approach. Neither medication assures weight loss; results depend on adherence, lifestyle changes, and individual metabolism.
- 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 I get next day delivery for both Mounjaro and Wegovy in the UK?
Yes. Both are available through UK-registered online prescribing services that offer next day or express delivery. You'll need to complete an online clinical assessment with a UK-licensed prescriber before a prescription is issued. Delivery timescales vary by provider, so check with your chosen service for their specific delivery options.
Is Mounjaro more effective than Wegovy?
Clinical trial data shows Mounjaro produced slightly higher average weight loss (15–21% vs 15% for Wegovy), but this does not mean it will work better for you individually. Results vary significantly between people based on genetics, adherence, lifestyle, and other factors. Your prescriber will help choose the best option for your situation.
What are the main side effects of each medication?
Both share common side effects: nausea, diarrhoea, vomiting, constipation, and stomach pain—usually mild and temporary. These tend to improve as your body adjusts. Serious side effects are rare but can include severe stomach pain (possible pancreatitis) or gallbladder problems. Always report any concerning symptoms to your prescriber.
How long does dose titration take for Mounjaro vs Wegovy?
Mounjaro titration takes approximately 20 weeks to reach the maximum 15 mg dose (starting at 2.5 mg, increasing every 4 weeks). Wegovy titration takes approximately 16 weeks to reach 2.4 mg (starting at 0.25 mg). Both require minimum 4-week periods on each dose before escalation.
Do I need an NHS referral to get next day delivery Mounjaro or Wegovy?
No. Private UK prescribing services do not require an NHS referral. You can complete an online consultation directly with a licensed prescriber, and if approved, receive a prescription for next day delivery. NHS access requires specialist tier 3 weight management service referral from your GP, which involves longer waiting times in most regions.
Ready to take control of your weight loss journey?
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