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, Restless Legs, and Wegovy — What's the Difference?
Restless legs syndrome (RLS) is not a common side effect listed for either Mounjaro or Wegovy, but some individuals report discomfort when using GLP-1 and dual GIP/GLP-1 medications. If you're considering weight management treatment and have concerns about restless legs, it's important to understand how Mounjaro (tirzepatide) and Wegovy (semaglutide) differ in mechanism and reported effects. Both are prescription-only injections available in the UK, and both require a clinical assessment before prescription. This guide compares the two to help you have an informed conversation with your GP or prescriber.
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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 — Mechanism Differences
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist — it activates two natural hormone pathways simultaneously. This dual mechanism may affect how your body regulates appetite, glucose, and fat metabolism differently than a single GLP-1 agonist. Mounjaro uses a KwikPen device with doses ranging from 2.5 mg to 15 mg once weekly.
Wegovy (semaglutide) is a GLP-1 receptor agonist only — it targets a single pathway. This mechanism has been established in clinical practice for longer, with extensive trial data (STEP trials). Wegovy doses range from 0.25 mg to 2.4 mg once weekly.
The difference in mechanism means individual tolerability can vary. Some people report better tolerance with one over the other, though clinical trial data does not highlight restless legs as a frequent side effect of either medication. If you're experiencing restless leg symptoms, discuss with your prescriber whether your current medication might be contributing, or whether an alternative approach might be suitable.
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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.
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Clinical Trial Data and Individual Variation
The SURMOUNT-1 trial (Mounjaro) and STEP-1 trial (Wegovy) both tracked side effects carefully. Neither reported restless legs as a common or very common side effect. However, individual experiences vary significantly — some patients report muscle-related discomfort or unusual sensations when starting GLP-1 medications, whilst others do not.
If you develop restless legs or similar symptoms after starting either medication, your prescriber may suggest: adjusting the dose, allowing more time for your body to adapt, ensuring adequate sleep and hydration, or switching to the alternative medication. Use our free GLP-1 weight loss calculator to explore potential outcomes with different medications, and discuss any side effect concerns with your GP or prescriber before making changes. They can assess whether the symptom is medication-related or linked to other factors such as diet changes, activity levels, or underlying conditions like iron deficiency.
- 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 restless legs a known side effect of Mounjaro?
Restless legs syndrome is not listed as a common or very common side effect in Mounjaro clinical trials or product information. However, some individuals report unusual sensations or mild discomfort when starting GLP-1 medications. If this occurs, inform your prescriber immediately.
Does Wegovy cause restless legs more or less than Mounjaro?
Neither medication lists restless legs as a frequent side effect. There is no clinical evidence that Wegovy causes this more or less than Mounjaro. Individual tolerance varies, and prescriber guidance is essential if symptoms develop.
Can I switch from Mounjaro to Wegovy if I experience restless legs?
Possibly, but only with your prescriber's guidance. They may first explore whether the symptom is truly medication-related or linked to other factors such as iron levels, sleep quality, or diet changes. A switch requires a clinical reassessment and dose adjustment plan.
What should I do if I develop restless legs while taking either injection?
Contact your GP or prescriber immediately. Do not stop the medication without guidance. Your prescriber will assess the cause, which may be unrelated to the medication, and advise on next steps — which might include dose adjustment, adding support, or a gradual switch to an alternative.
Are there any dietary or lifestyle measures that help with restless legs?
Yes. Ensure adequate sleep, hydration, and iron intake. Reduce caffeine and alcohol. Gentle exercise may help. Your GP can check for iron deficiency or other underlying causes. These measures may reduce symptoms regardless of weight management medication.
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