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 7.5 mg vs Wegovy: How They Compare
If you're considering weight loss injections in the UK, you may have heard about both Mounjaro and Wegovy. Both are prescription-only medications approved for weight management, but they work differently and have distinct profiles. This guide compares Mounjaro 7.5 mg—a mid-range dose of the dual GIP and GLP-1 agonist tirzepatide—with Wegovy (semaglutide), a GLP-1-only medication. Understanding the differences helps you and your prescriber decide which might suit your individual health needs.
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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 7.5 mg and Wegovy Work Differently
Mounjaro (tirzepatide) activates two hormone pathways: GIP (glucose-dependent insulinotropic polypeptide) and GLP-1 (glucagon-like peptide-1). This dual mechanism may help regulate appetite, reduce cravings, and support feeling fuller after meals. At 7.5 mg, you're at an escalation dose within Mounjaro's titration schedule, which typically progresses from 2.5 mg to a maximum of 15 mg.
Wegovy (semaglutide) targets only the GLP-1 pathway. It has a single mechanism but is well-established in clinical practice, with the maximum maintenance dose of 2.4 mg. Both medications slow gastric emptying (how quickly food leaves your stomach), though this effect often reduces over time.
- Mounjaro KwikPen: Once-weekly injection, pre-filled, maximum 15 mg dose
- Wegovy pen: Once-weekly injection, pre-filled, maximum 2.4 mg dose
- Mechanism: Mounjaro dual action vs Wegovy single GLP-1 action
The dual mechanism of Mounjaro may offer an advantage in weight loss for some people, though individual responses vary significantly.
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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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Clinical Trial Data and Individual Variation
In the SURMOUNT-1 clinical trial, Mounjaro 7.5 mg resulted in an average weight loss of approximately 19.5% of body weight over 72 weeks when combined with diet and exercise. Wegovy's STEP-1 trial showed approximately 14.9% average weight loss at the maximum 2.4 mg dose over 68 weeks. However, individual results vary considerably—some people lose significantly more or less than the average. Your prescriber will assess your personal circumstances, medical history, and weight-related conditions to determine which medication (if either) is most suitable for you. Both require ongoing clinical assessment and a prescription following a thorough health evaluation. Use our GLP-1 weight loss calculator above to see projected weight loss ranges at different doses and understand what may be realistic 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 7.5 mg more effective than Wegovy?
Clinical trials suggest Mounjaro may deliver slightly greater average weight loss than Wegovy, but individual results vary greatly. Neither medication works the same way for everyone. Your prescriber will choose based on your health profile, not trial averages. Effectiveness also depends on your commitment to diet and exercise changes.
Can I switch from Mounjaro to Wegovy or vice versa?
Some people do switch between GLP-1 medications, but this requires your prescriber's guidance. There's no official dose equivalence chart—approximate switches are roughly Mounjaro 5 mg ≈ Wegovy 0.5 mg, and Mounjaro 15 mg ≈ Wegovy 2.4 mg. Any switch must be managed carefully by a licensed prescriber.
What's the difference between Mounjaro KwikPen and Wegovy pens?
Both are once-weekly pre-filled injections. The KwikPen is Mounjaro's delivery device. Wegovy uses Novo Nordisk's standard pen design. Both are injected under the skin (abdomen, thigh, or upper arm). Storage and handling are similar—refrigerate unopened, room temperature after first use for up to 30 days.
How do I know if I'm eligible for Mounjaro 7.5 mg or Wegovy in the UK?
Both are available to UK adults with a BMI of 30 or above, or BMI 27–29.9 with weight-related health conditions (diabetes, hypertension, cardiovascular disease). South Asian, Black African, and Caribbean adults may qualify at lower BMIs. Your GP or a licensed prescriber will assess your individual eligibility.
Which medication is available on the NHS in the UK?
NICE has approved tirzepatide (Mounjaro) within NHS specialist tier 3 weight management services, with significant regional variation in availability. Both Mounjaro and Wegovy are available privately through GPhC-registered online pharmacies following clinical assessment. NHS access typically requires a GP referral to specialist services, which may have waiting lists.
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