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 and Sensitive Skin — What You Need to Know
If you have sensitive skin and are considering Mounjaro (tirzepatide), you may be wondering whether injection site reactions are common or how your skin type might affect tolerability. Both Mounjaro and Wegovy can cause localised injection site reactions, though these are typically mild and temporary. Understanding what to expect, how injection site sensitivity differs between the two medications, and practical steps to minimise discomfort can help you make an informed decision with your prescriber. Our GLP-1 weight loss calculator can help you explore potential outcomes, whilst our BMI calculator shows your current health baseline before starting any treatment.
10,000+ calculations today · NHS-aligned thresholds · 100% free
Calculate Your BMI Instantly
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 Affect Sensitive Skin
Injection site reactions are among the most common side effects of both Mounjaro and Wegovy, though they are usually mild and resolve within hours to days. With Mounjaro, clinical trial data shows that injection site reactions (redness, bruising, itching, or mild pain at the injection site) occurred in approximately 10–15% of participants. Wegovy shows similar frequencies in the STEP trials. The key difference is injection frequency and needle gauge: Mounjaro is a once-weekly injection with a slightly larger needle than Wegovy's auto-injector pen, which may result in slightly more noticeable local reactions in some people with very sensitive skin. However, individual response varies significantly. People with conditions like eczema, psoriasis, or dermatitis may experience more pronounced reactions, though this does not necessarily mean Mounjaro is unsuitable — it simply requires closer monitoring and good injection technique.
- Rotate injection sites weekly to avoid repeated trauma to the same area
- Allow injections to reach room temperature before administering
- Avoid injecting into areas of active skin inflammation or rash
- Use an ice pack 30 seconds before injection to reduce discomfort (optional)
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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.
Free Weight Loss Tools & Guides
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
Mounjaro vs Wegovy — Mechanism and Skin Sensitivity
Mounjaro is a dual GIP and GLP-1 receptor agonist, whilst Wegovy is a GLP-1 agonist only. This difference in mechanism does not directly affect injection site sensitivity — both medications have similar rates of local reactions. However, Mounjaro starts at a lower dose (2.5 mg) and titrates more gradually than Wegovy, which may theoretically give your skin time to adapt to the injection itself. Wegovy's dose escalation schedule is also gradual but begins from a higher starting point (0.25 mg). Neither medication is intrinsically safer for sensitive skin; the choice depends on your individual prescriber assessment, overall health profile, BMI, and any weight-related comorbidities. Your GP or licensed prescriber will determine which is most appropriate after a clinical evaluation.
If you have a known skin condition or significant injection site sensitivity, mention this during your clinical assessment. Your prescriber may recommend strategies such as alternating injection sites more frequently, using topical anaesthetic cream (though this is not standard practice), or — in rare cases — choosing an alternative weight management approach. Minor injection site reactions typically do not require stopping the medication; they usually resolve within 24–48 hours. If you develop signs of infection (increasing warmth, pus, spreading redness) or a serious allergic reaction affecting the face or throat, seek immediate medical attention. Track your progress and any skin reactions using our free progress tracker, which can help you and your prescriber identify patterns and make informed adjustments to your treatment plan.
- 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.
Does Mounjaro cause more injection site reactions than Wegovy?
Clinical trial data shows similar rates of injection site reactions between Mounjaro and Wegovy (approximately 10–15% of participants). Mounjaro uses a slightly larger needle, which some people perceive as more uncomfortable, but actual reaction rates are comparable. Individual experience varies based on skin sensitivity and injection technique. Your prescriber will help determine which is better suited to you.
Can I use Mounjaro if I have eczema or psoriasis?
Yes, Mounjaro can typically be used with eczema or psoriasis, but you should inform your prescriber about your skin condition during assessment. Avoid injecting into areas of active inflammation. Minor injection site reactions are expected but usually resolve quickly. If you experience severe or worsening skin reactions, contact your GP.
What should I do if I develop a rash or severe redness after a Mounjaro injection?
Minor redness and slight bruising are normal and typically fade within 24–48 hours. If redness spreads, worsens, or you develop signs of infection (warmth, pus, swelling), contact your GP. Serious allergic reactions affecting your face, lips, or throat require immediate medical attention — call 999.
Is Wegovy better than Mounjaro for people with sensitive skin?
Neither medication is inherently better for sensitive skin — both have similar injection site reaction rates. Wegovy uses an auto-injector pen which some find easier to use, whilst Mounjaro uses a KwikPen. Your prescriber will assess your individual circumstances, skin condition, and overall health to recommend the most suitable option after a clinical evaluation.
Can I reduce injection site reactions by changing my technique?
Yes. Rotate injection sites weekly (abdomen, upper thigh, upper arm), ensure the pen is room temperature, and avoid injecting into areas with active skin inflammation. Allow 30 seconds between successive injections if using the same area. Good technique significantly reduces discomfort and local reactions in most people.
Ready to take control of your weight loss journey?
Start with a free BMI check, explore your GLP-1 options, or begin tracking your progress today. No sign-up. No cost. Just results.