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 Sunbeds — What You Need to Know
If you're taking Mounjaro (tirzepatide) and wondering whether it's safe to use sunbeds, this guide covers the key considerations. Mounjaro can affect how your skin responds to UV exposure, and understanding these risks is important for your health. We'll explain the connection between GLP-1 and GIP receptor agonists like tirzepatide and skin sensitivity, compare this with Wegovy (semaglutide), and help you make informed decisions about sun exposure whilst on weight loss treatment.
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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.
Mounjaro, UV Exposure, and Skin Sensitivity
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist that may increase skin sensitivity to sunlight and UV radiation. Whilst not explicitly listed as a photosensitising medication in standard references, some users report increased skin reactions to sun exposure during treatment. The mechanism isn't fully understood, but it may relate to how the medication affects skin metabolism and inflammatory responses.
Common GLP-1 and GIP/GLP-1 side effects include changes to skin appearance, including hair loss (alopecia) and changes in skin texture. These factors combined suggest that protecting your skin from UV exposure is sensible whilst on Mounjaro. Sunbeds emit high-intensity UVA and UVB radiation — significantly more concentrated than natural sunlight — making them a higher-risk activity if your skin is already sensitised. The NHS recommends limiting all UV exposure, particularly for people taking medications that may affect skin health. If you're using our GLP-1 weight loss calculator to track progress on Mounjaro, it's equally important to track your sun exposure and skin health during treatment.
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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 — Sunbed Safety Comparison
Both Mounjaro and Wegovy are prescription-only weight loss injections licensed in the UK, but they work differently. Mounjaro is a dual GIP/GLP-1 agonist, whilst Wegovy (semaglutide) is a GLP-1-only agonist. Neither medication is specifically noted to cause photosensitivity in clinical trials, yet both can trigger skin-related side effects including changes in skin condition and hair loss.
The key difference: Mounjaro's dual mechanism may theoretically have a broader systemic impact on skin health compared to Wegovy's single GLP-1 pathway. However, individual responses vary significantly. Both medications require a prescription and clinical assessment before use. If sun sensitivity or skin health is a concern for you, discuss this with your prescriber when seeking your mounjaro UK prescription — they can advise whether Mounjaro or Wegovy is more suitable, and provide personalised guidance on UV protection during treatment with tirzepatide or semaglutide.
- 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 I use sunbeds whilst taking Mounjaro?
Sunbeds are not recommended whilst taking Mounjaro. The medication may increase skin sensitivity to UV radiation, and sunbeds emit concentrated UVA/UVB that could trigger adverse skin reactions. Stick to natural sunlight with high SPF protection, or avoid UV exposure altogether during treatment. Always check with your prescriber for personalised advice.
Does Mounjaro cause photosensitivity?
Mounjaro isn't listed as a photosensitising medication, but users report increased skin sensitivity during treatment. This may relate to side effects like hair loss and skin texture changes. Until more data is available, it's sensible to assume increased sun sensitivity and protect your skin accordingly with high SPF sunscreen.
Is Wegovy safer for sunbed use than Mounjaro?
Wegovy (semaglutide) and Mounjaro (tirzepatide) both carry potential skin-related side effects. Neither is ideal for frequent sunbed use. Wegovy's single GLP-1 mechanism may theoretically have less systemic impact, but individual responses vary. Both require clinical assessment — your prescriber can advise based on your specific health profile.
What's the safest sun protection whilst on Mounjaro?
Use high SPF (50+) broad-spectrum sunscreen daily, reapply every 2 hours, wear protective clothing (hats, long sleeves), and avoid peak UV hours (11am–3pm). Avoid sunbeds and intense sun exposure. Consider vitamin D supplementation if you're limiting sunlight. Discuss sun safety with your GP or prescriber during mounjaro dose titration.
Should I stop Mounjaro if I want to use sunbeds?
Do not stop Mounjaro without medical guidance. If sunbed use is important to you, discuss alternatives with your prescriber before starting treatment. They may suggest Wegovy or another option, or advise on timing your UV exposure around your mounjaro UK prescription schedule. Individual risk and benefits will be assessed during your clinical assessment.
Ready to take control of your weight loss journey?
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