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 Psoriasis — What the Evidence Shows
Mounjaro (tirzepatide) is a prescription-only GLP-1 and GIP receptor agonist used for weight management in the UK. If you have psoriasis or a family history of skin conditions, you may be concerned about how Mounjaro could affect your skin. This guide explains what current evidence shows about the link between tirzepatide and psoriasis, and what you should discuss with your GP before starting this medication.
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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.
What Does the Evidence Say About Mounjaro and Psoriasis?
Clinical trials for Mounjaro, such as the SURMOUNT studies, did not identify psoriasis or psoriasis flares as common side effects. Psoriasis is not listed in the official product information as a known risk. However, GLP-1 and GIP receptor agonists are relatively new medications, and long-term skin-related effects in real-world use continue to be monitored.
- Psoriasis involves immune system activation — Mounjaro does not directly suppress or activate the immune system in ways known to trigger psoriasis
- Some GLP-1 medications have been associated with rare reports of autoimmune flares in other conditions, though causation is not proven
- Individual skin responses vary widely, and pre-existing skin conditions can be unpredictable when starting new medications
- The MHRA actively monitors Mounjaro (Black Triangle ▼ status) for emerging safety signals, including skin reactions
If you have psoriasis and are considering Mounjaro, your prescriber needs to assess your individual risk versus benefit.
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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.
What You Should Tell Your GP or Prescriber
Always disclose any history of psoriasis, eczema, or other autoimmune skin conditions before starting Mounjaro. Your GP or online prescriber uses this information to decide whether the medication is safe for you. If you develop a new skin rash, itching, or worsening of existing psoriasis after starting Mounjaro, contact your healthcare provider immediately — do not assume it is unrelated.
Monitor your skin during the first weeks of treatment and keep a record of any changes. Some people may need to pause or discontinue Mounjaro if skin symptoms worsen. Your prescriber can also check whether other weight management approaches or medications might be safer for your individual situation.
- 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 psoriasis?
No. Psoriasis is not listed as a common side effect in clinical trials or product information for Mounjaro. However, because GLP-1 and GIP medications are relatively new, long-term skin effects are still being monitored. If you develop new skin symptoms after starting Mounjaro, discuss this with your GP immediately.
Can Mounjaro make existing psoriasis worse?
Mounjaro is not known to worsen psoriasis, but individual responses vary. Since psoriasis involves immune system activity, any new medication warrants caution. Always inform your prescriber of existing psoriasis before starting treatment so they can monitor you.
What should I do if my psoriasis flares after starting Mounjaro?
Contact your GP or the prescriber who issued your Mounjaro prescription straight away. Do not assume the flare is unrelated to the medication. Your doctor can assess whether Mounjaro is responsible and discuss whether continuing, pausing, or stopping the medication is appropriate.
Is it safe to use Mounjaro if I have a family history of psoriasis?
Family history of psoriasis does not automatically mean you cannot take Mounjaro. Your prescriber will assess your individual risk based on your personal and family history, current health, and other factors. Be transparent with them about your family background.
Can I calculate my BMI and weight loss goals if I have psoriasis and want to try Mounjaro?
Yes. Use our free BMI calculator to check your starting weight and BMI — this information is useful when discussing Mounjaro eligibility with your GP. You can also use our GLP-1 weight loss calculator to see projected outcomes, though individual results vary and skin safety remains the priority.
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.