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 Neck Pain vs Wegovy: What's the Difference?
Neck pain and muscle discomfort can occur with both Mounjaro (tirzepatide) and Wegovy (semaglutide), but they affect users differently. This guide compares both medications side-by-side, looking at how they work, what clinical trials showed about side effects, and how your GP or prescriber decides which is right for you. Both are prescription-only weight management injections licensed in the UK — but understanding their differences helps you have an informed conversation with your healthcare team.
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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.
Mounjaro vs Wegovy: Clinical Trial Data and Mechanism Differences
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist — it activates two hormone pathways, which may explain why it produces slightly higher average weight loss in trials. The SURMOUNT-1 trial showed average weight loss of around 20.9% at the maximum 15 mg dose. Neck pain and muscle aches were reported but not listed as "very common" side effects.
Wegovy (semaglutide) is a GLP-1 receptor agonist only — it activates one pathway. The STEP-1 trial showed average weight loss of approximately 14.9% at the maximum 2.4 mg dose. Side effect profiles were similar to Mounjaro, including occasional reports of muscle-related discomfort.
- Both are once-weekly injections
- Both work by reducing appetite and increasing fullness signals
- Individual side effect experiences vary significantly
- Neck pain is not a primary or "very common" side effect for either
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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 Is Right for You? The Role of Clinical Assessment
Neither Mounjaro nor Wegovy is universally "better" — suitability depends on your individual health profile, medical history, current medications, and how your body responds. If you experience neck pain or muscle discomfort on one medication, your prescriber may suggest switching to the other, adjusting your dose, or exploring whether the symptom is related to the injection itself or another factor like posture or activity changes.
Both medications require a UK prescription and clinical assessment before being prescribed. Your GP or a licensed online prescriber will review your BMI, weight-related health conditions, allergies, and current medications to decide which is appropriate for you. Use our free BMI calculator to check your personal BMI, and discuss the results with your prescriber as part of your eligibility assessment.
- 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 Mounjaro cause neck pain?
Neck pain is not listed as a common or very common side effect of Mounjaro in clinical trials. However, some users report muscle aches or discomfort. This may be related to posture changes, activity levels, or injection technique rather than the medication itself. If you experience persistent neck pain, inform your GP or prescriber.
Is neck pain more common with Wegovy than Mounjaro?
Clinical trial data does not show significant differences in neck or muscle pain between Wegovy and Mounjaro. Both medications can cause general muscle discomfort in some users, but it is not a primary side effect for either. Individual responses vary considerably.
What are the most common side effects of both medications?
The most common side effects for both Mounjaro and Wegovy are nausea, diarrhoea, vomiting, constipation, and stomach pain — particularly when starting or increasing doses. These often improve over time as your body adjusts.
How do I know which injection to choose — Mounjaro or Wegovy?
Your prescriber will assess your individual health needs, medical history, and BMI to recommend the most suitable option. Both are prescription-only and require a clinical assessment. Neither is universally better — it depends on your unique circumstances.
Can I switch from Mounjaro to Wegovy if I experience side effects?
Yes, switching between medications is possible if one causes bothersome side effects. This decision must be made with your prescriber, who will manage the transition safely. Some side effects improve with time or dose adjustment before switching is necessary.
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.