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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Is Itching a Side Effect of Mounjaro?
Itching (pruritus) is not listed as a common or very common side effect of Mounjaro in the UK product information, though some people taking this prescription-only weight management injection report experiencing skin irritation. If you develop itching while taking Mounjaro, it's important to understand whether it's related to the medication itself, an injection site reaction, or something else entirely. This guide explains what the clinical evidence shows, when to contact your GP, and practical steps you can take. Always speak with your prescriber if side effects concern you.
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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/mยฒ).
While BMI isn't a perfect measure โ it doesn't account for muscle mass, bone density, or fat distribution โ 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 โ 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.
What Does the Clinical Evidence Show About Mounjaro and Itching?
Itching is not listed as a very common or common side effect in the official UK product information for Mounjaro (tirzepatide). The most frequently reported side effects in clinical trials were nausea, diarrhoea, vomiting, and constipation โ gastrointestinal effects linked to how tirzepatide works as a dual GIP and GLP-1 receptor agonist.
However, some people taking Mounjaro do report skin-related symptoms. These may include:
- Injection site reactions: Localised redness, bruising, pain, or mild itching at the injection site โ these are common and typically resolve within a few days.
- Allergic reactions: Rare but serious; seek immediate medical attention if you develop facial swelling, throat tightness, or severe itching shortly after injection.
- Unrelated skin conditions: Itching unrelated to Mounjaro, coinciding with starting the medication, may be due to other causes (dry skin, contact dermatitis, eczema flare-up).
If your itching is severe, persistent, or accompanied by other symptoms, contact your GP or the prescriber who issued your Mounjaro prescription.
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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 โ all stored privately in your browser.
Free Weight Loss Tools & Guides
Everything you need to understand your weight, explore medication options, and track your progress โ completely free.
When Should You Contact Your GP About Itching?
Seek medical advice immediately if itching is accompanied by facial swelling, difficulty breathing, hives, or signs of a serious allergic reaction โ these are emergencies requiring urgent care.
Contact your GP or prescriber within 48 hours if itching is severe, spreading, or affecting your daily life. Also reach out if itching develops alongside other new symptoms like rash, fever, or unusual bruising.
For mild injection site itching that resolves within a few days, this is typically normal and does not require medical attention. You can manage it with cool compresses or over-the-counter moisturiser (ask your pharmacist for suitable options). Keep a record of when itching occurs and what it feels like โ this helps your GP or prescriber assess whether it's related to Mounjaro or another cause. Track your symptoms using our free progress tracker to share patterns with your healthcare team.
- 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 โ 5mg โ 7.5mg โ 10mg โ 12.5mg โ 15mg
- GLP-1 receptor agonist
- Up to 15โ17% body weight loss (STEP trials)
- Weekly injection, 5-step dose escalation
- NHS & private prescription available
- Doses: 0.25mg โ 0.5mg โ 1mg โ 1.7mg โ 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 | 15โ22.5% | 12โ17% |
| Key trial | SURMOUNT-1 (2022) | STEP 1 (2021) |
| Max dose | 15 mg weekly | 2.4 mg weekly |
| Escalation period | 20โ32 weeks | 16โ20 weeks |
| Administration | Weekly injection (pen) | Weekly injection (pen) |
| NHS availability | Private prescription only | NHS & private |
| Approx. private cost | ยฃ150โยฃ250/month | ยฃ150โยฃ300/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 โ 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 itching a listed side effect of Mounjaro in the UK?
Itching (pruritus) is not classified as a very common or common side effect in the official UK product information for Mounjaro. The most common side effects are gastrointestinal (nausea, diarrhoea, vomiting, constipation). However, some people report skin-related symptoms, which may include mild injection site itching or, rarely, allergic reactions requiring urgent medical attention.
What's the difference between injection site itching and an allergic reaction?
Injection site itching is mild, localised to the injection area, and typically resolves within a few days. Allergic reactions are rare but serious, causing facial swelling, throat tightness, difficulty breathing, hives, or severe itching developing within minutes to hours of injection. Allergic reactions need immediate emergency care.
Can Mounjaro cause itching anywhere on the body, not just at the injection site?
Itching beyond the injection site is not a typical side effect listed in clinical trials. If you develop generalised itching while taking Mounjaro, it may be unrelated to the medication โ caused by dry skin, eczema, contact dermatitis, or another condition. Your GP can help determine the cause and recommend appropriate treatment.
How should I manage mild injection site itching while taking Mounjaro?
For mild localised itching, try cool compresses, avoid scratching, and apply a fragrance-free moisturiser. Rotate your injection sites weekly to reduce irritation. If itching persists beyond a few days, worsens, or spreads, contact your prescriber. Do not stop Mounjaro without medical guidance.
Should I stop taking Mounjaro if I develop itching?
No โ do not stop Mounjaro without speaking to your prescriber first. Mild injection site itching usually resolves naturally. If itching is severe or you suspect an allergic reaction, seek urgent medical help immediately. Your prescriber can advise whether continuing or adjusting your treatment is appropriate for your situation.
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