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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Is Mounjaro Semaglutide? Key Differences Explained
No, Mounjaro is not semaglutide — they are two different medications. Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, whilst semaglutide is sold as Wegovy for weight management in the UK. Understanding the difference is important if you're exploring prescription weight loss options. Both are once-weekly injections, both require a prescription, but they work through different mechanisms and have different costs and availability across NHS and private routes 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.
The Key Difference: Mounjaro vs Semaglutide
Mounjaro (tirzepatide) activates two hormone pathways: GIP (glucose-dependent insulinotropic polypeptide) and GLP-1. This dual action is what sets it apart from semaglutide-based medications. In clinical trials, this dual mechanism was associated with an average weight loss of approximately 15–21% of body weight over 72 weeks, though individual results vary significantly.
Semaglutide (Wegovy) activates only the GLP-1 pathway. Whilst still effective, semaglutide works through a single mechanism, and clinical trial data showed average weight loss of around 14.9% of body weight at 68 weeks. Both medications slow gastric emptying and help reduce appetite, but the dual action of Mounjaro may provide additional metabolic support.
- Mounjaro: dual GIP + GLP-1 agonist, maximum dose 15 mg weekly
- Wegovy (semaglutide): GLP-1 agonist only, maximum dose 2.4 mg weekly
- Both require a prescription and clinical assessment before use
- Both are once-weekly injections delivered via pre-filled pens (Mounjaro uses a KwikPen)
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.
UK Cost and Access Routes: NHS vs Private
NHS access: Both Mounjaro and semaglutide (Wegovy) are available through NHS specialist weight management services in tier 3 or tier 4 settings. However, NHS availability varies significantly by region — some areas have long waiting lists, and access depends on meeting eligibility criteria and referral from your GP. NHS prescribing does not involve direct cost to you at the point of dispensing (standard prescription charges apply if you pay per item).
Private access: Both medications are available through UK-licensed online prescribing services following a clinical assessment. Private costs typically range from £129 to £320+ per month depending on the dose and provider. You will require a valid UK prescription from a licensed prescriber. Use our free GLP-1 weight loss calculator to explore potential outcomes, and our BMI calculator to check your current health metrics before consultation.
Online consultation process: When accessing either Mounjaro or semaglutide privately, you'll complete a medical questionnaire, be assessed by a UK-licensed prescriber, and receive a prescription if suitable. The medication is then dispensed by a GPhC-registered pharmacy and delivered to your address. This typically takes 2–5 working days. No in-person appointment is required, but the prescriber may ask follow-up questions about your medical history, current medications, and weight management goals.
Important eligibility note: Both medications require a BMI of 30 kg/m² or above, or BMI 27–29.9 kg/m² with weight-related health conditions such as type 2 diabetes, hypertension, or cardiovascular disease. For people of South Asian, Chinese, Black African, or Black Caribbean heritage, lower thresholds may apply (BMI 27.5+). Your GP or prescriber will assess whether either medication is clinically appropriate for you.
- 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 Mounjaro the same as semaglutide?
No. Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, whilst semaglutide (Wegovy) activates only the GLP-1 pathway. Both are prescription-only weight management injections available in the UK, but they work through different mechanisms. Clinical trial data suggests Mounjaro may produce slightly higher average weight loss (15–21% vs 14.9%), though individual results vary.
What's the typical cost of Mounjaro or semaglutide in the UK?
Private costs typically range from £129 to £320+ per month depending on dose and provider. NHS access is free at point of dispensing (standard prescription charges may apply) but varies by region and requires referral to specialist weight management services. Waiting times for NHS access can be several months to over a year in some areas.
Can I get Mounjaro or semaglutide through my GP?
Not directly from your GP surgery. Both medications are prescribed through tier 3 or tier 4 NHS specialist weight management services after GP referral, or through private UK-licensed online prescribing services. Your GP cannot prescribe them in primary care, but can refer you to specialist services if you're eligible.
How long does it take to receive Mounjaro or semaglutide if I go private?
Once you've completed an online clinical assessment and received a prescription (usually within 24–48 hours), the medication is typically dispatched and delivered within 2–5 working days. NHS routes involve longer waits due to referral and specialist appointment processes, which can take weeks to months depending on your local ICB.
Which is more effective — Mounjaro or semaglutide?
Clinical trials showed Mounjaro produced average weight loss of 15–21%, whilst semaglutide averaged 14.9%. However, individual results vary significantly based on dose, adherence, diet, and activity level. A prescriber can help you choose which is more suitable based on your personal health profile and medical history. Neither assures specific weight loss outcomes.
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.