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 Shoulder Pain vs Wegovy: What You Need to Know
Shoulder pain is not commonly reported with either Mounjaro or Wegovy, though both medications can cause various side effects. This guide compares the two prescription-only weight management injections used in the UK, explaining how they work differently, what clinical trials showed, and why individual experiences vary. Both require a clinical assessment and prescription from a licensed healthcare professional before use.
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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 Differ in Mechanism and Side Effects
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, whereas Wegovy (semaglutide) is a GLP-1 agonist only. This dual mechanism may explain some differences in how people experience side effects. Both medications can cause gastrointestinal effects like nausea, diarrhoea, and constipation—these are the most commonly reported side effects in UK prescribing practice.
The SURMOUNT clinical trials for Mounjaro and the STEP trials for Wegovy documented nausea, vomiting, and stomach pain as very common side effects affecting more than 1 in 10 people. Shoulder pain specifically was not highlighted as a primary concern in either trial dataset. When shoulder discomfort does occur during weight management treatment, it is more likely related to injection technique, site rotation, or coincidental musculoskeletal issues rather than the medication itself.
Using the GLP-1 weight loss calculator on this page can help you explore projected outcomes at different doses, allowing you to discuss realistic expectations with your prescriber before starting either medication.
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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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Individual Suitability and Clinical Assessment
Whether Mounjaro or Wegovy is prescribed depends entirely on individual clinical assessment, not on side effect comparisons. Your GP or licensed prescriber will assess your medical history, current medications, BMI, and weight-related health conditions to determine which is appropriate for you. Both are available through NHS specialist weight management services or via private prescription after online clinical assessment.
Eligibility for both medications is the same in the UK: BMI of 30 kg/m² or above, or 27–29.9 with weight-related conditions such as type 2 diabetes, high blood pressure, or sleep apnoea. South Asian, Chinese, Black African, or Black Caribbean adults may be eligible at BMI 27.5 or above due to higher health risks at lower BMI levels. Neither medication is assured to work identically for all users—individual results vary significantly based on lifestyle, diet, metabolism, and adherence.
Q1: Is shoulder pain a known side effect of Mounjaro? A1: Shoulder pain is not listed as a common or very common side effect of Mounjaro in clinical trials or UK prescribing information. The most frequently reported side effects are gastrointestinal (nausea, diarrhoea, vomiting, constipation). If you experience shoulder pain while using Mounjaro, it may be unrelated to the medication—discuss it with your GP to rule out other causes like musculoskeletal issues or injection technique problems. Q2: Does Wegovy cause shoulder pain more or less than Mounjaro? A2: Shoulder pain is not a documented side effect of Wegovy either. Both medications focus on gastrointestinal side effects in clinical data. Any shoulder discomfort during weight management treatment should be evaluated by your GP independently of the medication itself. Proper injection technique and site rotation (stomach, thigh, upper arm) can help prevent injection-related discomfort. Q3: What are the most common side effects of both Mounjaro and Wegovy? A3: Both medications commonly cause nausea, diarrhoea, vomiting, and constipation—especially when starting or increasing doses. These typically improve over time as your body adjusts. Less common side effects include headache, fatigue, and indigestion. Your prescriber will discuss how to manage these effects and when to seek medical attention. Q4: Should I choose Mounjaro or Wegovy based on side effect profiles? A4: Side effect profiles are very similar between the two medications. Your prescriber will recommend one based on your clinical assessment, medical history, and eligibility—not primarily on side effect comparison. Both require a prescription and clinical judgment. If you experience side effects on one, your prescriber may adjust the dose or consider an alternative approach rather than switching medications. Q5: Can I use the BMI calculator to check my eligibility for either medication? A5: Yes—use our free BMI calculator on this page to check your BMI instantly. However, eligibility for Mounjaro or Wegovy also depends on weight-related health conditions and individual clinical assessment. A BMI in the eligible range (30+, or 27+ with conditions) is necessary but not sufficient—you'll need to discuss your full health picture with your GP or a licensed 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.
What is BMI and how is it calculated?
BMI (Body Mass Index) is calculated by dividing your weight in kilograms by your height in metres squared. It's the standard screening tool used by the NHS to assess whether adults are a healthy weight.
Is BMI accurate for everyone?
BMI is a useful screening tool but doesn't account for muscle mass, bone density, or body fat distribution. Athletes may have a high BMI without excess fat. The NHS recommends using BMI alongside waist circumference for a more complete picture.
What are GLP-1 medications like Mounjaro and Wegovy?
GLP-1 receptor agonists are prescription medications that mimic gut hormones to reduce appetite and help with weight loss. Mounjaro (tirzepatide) and Wegovy (semaglutide) are the two most widely used for weight management in the UK.
Am I eligible for GLP-1 weight loss medication in the UK?
Generally, you need a BMI of 30+ (obese) or 27+ with a weight-related health condition. You must be 18 or over. Use our BMI calculator to check.
What is the difference between Mounjaro and Wegovy?
Mounjaro (tirzepatide) is a dual GIP/GLP-1 agonist with up to 22.5% weight loss. Wegovy (semaglutide) is GLP-1-only with up to 15-17% weight loss. Both are weekly injections.
Is this website free to use?
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Ready to take control of your weight loss journey?
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