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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Sensitive Skin and Mounjaro: What You Need to Know
If you have sensitive skin and are considering Mounjaro (tirzepatide), you may be wondering how this weight management injection might affect your skin. Injection site reactions are one of the most common side effects reported in clinical trials, but most are mild and manageable. This guide explains what to expect, how to minimise irritation, and when to contact your GP. All information is based on UK clinical data and NHS guidance.
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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.
Common Skin Reactions to Mounjaro
Injection site reactions are among the most frequently reported side effects of Mounjaro, though they occur in a small percentage of users. Common reactions include redness, itching, bruising, swelling, and mild pain at the injection site. These typically appear within hours of injection and usually resolve within a few days. The reactions are generally mild to moderate in severity and do not usually require treatment beyond basic care like ice or mild moisturiser. Bruising is more common in people with naturally sensitive or thin skin, or those taking blood thinners. Rotating your injection site each week—alternating between stomach, thigh, and upper arm—significantly reduces the risk of repeated irritation in the same area. If you have a history of keloid formation or hypertrophic scarring, inform your prescriber before starting Mounjaro, as they may recommend additional precautions or more frequent site rotation.
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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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Managing Sensitive Skin While Using Mounjaro
If your skin is naturally sensitive, several practical steps can help minimise Mounjaro injection reactions. Prepare injection sites by gently cleansing with mild soap and water 15 minutes before injection—avoid harsh antiseptics which can irritate sensitive skin. Allow the skin to dry completely before injecting. Use a fresh needle for each injection and inject slowly to reduce tissue trauma. After injection, avoid rubbing the area; instead, apply gentle pressure with clean gauze for a few seconds. For the following 24 hours, avoid tight clothing over the injection site, intense exercise, and hot baths or saunas, as heat can worsen inflammation. If itching or redness occurs, use a fragrance-free moisturiser or mild hydrocortisone cream (0.5–1%), but do not apply these before injection as they may affect absorption. Monitor the site for signs of infection such as increasing warmth, pus, or spreading redness, and contact your GP if these develop.
- 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 allergic reactions on the skin?
Serious allergic reactions to tirzepatide are rare but possible. Signs include severe swelling of the face, lips, or throat, widespread rash, or difficulty breathing—seek emergency care immediately if these occur. Minor skin reactions like localised redness or itching are not true allergies but are irritation from the injection itself and are much more common.
Is it safe to use Mounjaro if I have eczema or dermatitis?
Yes, but with care. Avoid injecting directly into areas of active eczema or dermatitis, as broken or inflamed skin may be more sensitive to injection trauma. Choose unaffected areas on your stomach or thigh. Inform your prescriber about your skin condition so they can monitor your suitability for the medication and offer additional guidance.
Will Mounjaro cause permanent scarring if I use it long-term?
Permanent scarring from Mounjaro injections is very rare, especially with proper site rotation and gentle injection technique. Most injection site reactions resolve completely without scarring. The risk of keloid or scar formation is similar to that of any injection therapy and is lower if you rotate sites regularly.
How long do injection site reactions typically last?
Most mild reactions—redness, swelling, bruising—resolve within 24 to 72 hours. Some bruising may take up to 1–2 weeks to fade completely. If reactions persist beyond a week or worsen, contact your GP or the prescriber who issued your medication for advice.
Should I stop Mounjaro if I develop a skin reaction?
Mild injection site reactions do not usually require stopping treatment. However, if you develop signs of infection, severe persistent reactions, or are concerned about your symptoms, contact your prescriber or GP for guidance. They can assess whether your reaction is manageable or whether alternative approaches are needed.
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