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 vs Wegovy: Which Is Better for Sensitive Skin?
If you have sensitive skin and are considering weight loss injections, you may wonder whether Mounjaro or Wegovy is the better choice. Both are prescription-only GLP-1-based medications licensed in the UK for weight management, but they work slightly differently and may affect your skin differently. This guide compares the two medications specifically for sensitive skin concerns, helping you understand what to expect and what to discuss with your 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 Differently
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, meaning it activates two hormone pathways simultaneously. Wegovy (semaglutide) is a single GLP-1 receptor agonist, activating only one pathway. This difference in mechanism may influence how your body responds. In the SURMOUNT clinical trials, Mounjaro showed average weight loss of 15–21% of body weight, whilst Wegovy's STEP trials demonstrated approximately 15% average weight loss. Both are administered as once-weekly injections using a KwikPen. Mounjaro's dual mechanism may produce stronger appetite suppression, which some users report translates to fewer nausea-related symptoms over time, though individual responses vary significantly. Wegovy's single mechanism may be gentler for some users with sensitive systems, but clinical evidence does not definitively favour one over the other for skin sensitivity specifically.
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Injection Site Reactions and Sensitive Skin
Both Mounjaro and Wegovy can cause injection site reactions including redness, bruising, swelling, and itching—particularly common in people with sensitive skin. These reactions are usually mild and temporary, lasting a few hours to days. Key strategies to minimise reactions:
- Rotate injection sites weekly (stomach, thigh, or upper arm)
- Avoid injecting into the same spot repeatedly
- Allow skin to warm to room temperature before injection
- Use ice briefly before injection to numb the area
- Keep the injection site clean and dry
- Apply a fragrance-free moisturiser if irritation develops
Neither medication has a clear advantage for sensitive skin based on clinical data. Your prescriber can assess your individual skin sensitivity and help you choose the most suitable option, or monitor your response if you switch between them.
- 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 you use Mounjaro if you have very sensitive skin?
Yes, you can use Mounjaro with sensitive skin, though injection site reactions may be more noticeable. Common reactions include redness and mild itching at the injection site, which typically resolve within hours. Always inform your prescriber about your skin sensitivity before starting treatment so they can advise on injection techniques and aftercare. Rotating injection sites and allowing skin to reach room temperature before injection can help minimise reactions.
Is Wegovy or Mounjaro better for sensitive skin?
Neither medication has clinically proven superiority for sensitive skin specifically. Both can cause injection site reactions in people with sensitive skin. The choice between them depends on other factors including your BMI, weight-related health conditions, and individual response. Your prescriber will assess which is more suitable for you based on your overall health profile, not solely on skin sensitivity.
What injection site reactions should I expect with Mounjaro?
Common injection site reactions with Mounjaro include redness, bruising, pain, itching, and mild swelling—affecting more than 1 in 10 users. These are typically mild and temporary. Serious allergic reactions are rare but require immediate medical attention. Rotating your injection site each week and following proper injection technique minimises reactions. If reactions persist or worsen, contact your prescriber.
Can I switch from Mounjaro to Wegovy if my skin reacts badly?
Switching between medications is possible but must be managed by your prescriber. There is no official conversion chart between Mounjaro and Wegovy—your prescriber will determine the appropriate Wegovy dose based on your current Mounjaro dose and individual response. Never stop one medication and start another without medical guidance, as this may affect your weight management and health.
How do I reduce injection site irritation with weight loss injections?
Use these evidence-based techniques: rotate injection sites weekly between stomach, thigh, and upper arm; allow the pen to reach room temperature before injecting; clean the injection site with soap and water beforehand; apply ice for 10 seconds before injection to numb the area; and avoid injecting into irritated or bruised skin. Use fragrance-free moisturiser on any lingering irritation. If reactions intensify or don't improve within 48 hours, contact your GP or prescriber.
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