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: UK Online Ordering Guide
If you're looking to order Mounjaro online in the UK, you may be considering how it compares to Wegovy, the other main prescription weight loss injection available. Both are licensed for weight management in UK adults, but they work differently and have different doses, costs, and eligibility criteria. Understanding the key differences can help you decide which might be more suitable for your needs — though your prescriber will ultimately assess which is appropriate for you based on your individual health. This guide compares both medications factually, using clinical trial data and NHS guidance.
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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 Work Differently
The most important difference between Mounjaro and Wegovy is their mechanism of action. Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, meaning it activates two natural hormone pathways simultaneously. Wegovy (semaglutide) is a GLP-1 receptor agonist only, activating just one pathway. In clinical trials, this dual mechanism in Mounjaro was associated with greater average weight loss: SURMOUNT-1 trial data showed Mounjaro helped participants lose approximately 15–21% of body weight on average, whilst the STEP-1 trial showed Wegovy achieved approximately clinically studied weight loss on average. However, individual results vary significantly, and both medications work alongside reduced-calorie diet and increased physical activity. Mounjaro requires weekly injections (starting at 2.5 mg, up to 15 mg), whilst Wegovy also requires weekly injections but uses a different dose range (0.25 mg to 2.4 mg). Both are prescription-only and require a clinical assessment before ordering online through a UK-licensed prescriber.
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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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Eligibility, Side Effects, and Which Might Suit You
Both Mounjaro and Wegovy are prescribed for UK adults with a BMI of 30 or above, or BMI 27–29.9 with weight-related health conditions (such as type 2 diabetes, high blood pressure, or heart disease). Eligibility is assessed individually — your prescriber will review your health and determine which medication is suitable. Common side effects of both include nausea, diarrhoea, constipation, and stomach pain, though these often improve over time. Neither is suitable during pregnancy or breastfeeding. The choice between them depends on factors like individual response, side effect tolerance, and prescriber recommendation. Try our GLP-1 weight loss calculator to explore potential weight loss outcomes with either medication, and use our BMI calculator to check your current BMI and eligibility context before discussing options with your prescriber.
- 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 order Mounjaro online in the UK without a prescription?
No. Mounjaro is prescription-only and requires a prescription from a UK-licensed prescriber following a clinical assessment. You cannot order it without a valid prescription. Many UK-licensed online prescribing services can provide consultations and issue prescriptions if you are eligible — but assessment is mandatory.
Is Mounjaro better than Wegovy for weight loss?
Clinical trial data suggests Mounjaro may achieve slightly greater average weight loss (15–21% vs approximately 15% body weight) due to its dual mechanism. However, individual results vary considerably, and "better" depends on your personal response, side effects, and suitability. Your prescriber will recommend which is more appropriate for your specific health situation.
How long does it take to see results when ordering Mounjaro online?
Weight loss typically begins within the first few weeks, though results vary. Most people notice appetite changes within days of starting, but significant weight loss usually takes 8–12 weeks. Doses are increased gradually every 4 weeks, and maximum benefit is often seen at higher maintenance doses after several months.
What is the difference between Mounjaro's dose range and Wegovy's?
Mounjaro starts at 2.5 mg and increases to a maximum of 15 mg once weekly. Wegovy starts at 0.25 mg and increases to a maximum of 2.4 mg once weekly. Both require a minimum of 4 weeks at each dose before increasing. The doses are not directly comparable — they reflect different formulations and mechanisms.
Do I need NHS approval to order Mounjaro or Wegovy online privately?
No. Whilst both medications are available through NHS specialist services (with waiting lists and regional variation), you can order them privately through UK-licensed online prescribing services without NHS referral. However, you must still pass a clinical assessment and receive a valid prescription — a prescriber will review your health before issuing one.
Ready to take control of your weight loss journey?
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