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
Free tracker included with every download this week
Can You Take Mounjaro If You Have Type 1 Diabetes?
Mounjaro (tirzepatide) is not approved for use in people with type 1 diabetes in the UK. Unlike type 2 diabetes, where Mounjaro may be prescribed as part of weight management, type 1 requires different treatment approaches. This guide explains why type 1 and type 2 are a UK pharmacy differently, what the evidence shows, and what alternatives may be available if you have type 1 diabetes and need support with weight management.
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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.
Why Mounjaro Is Not Approved for Type 1 Diabetes
Mounjaro is specifically approved for adults with type 2 diabetes or weight-related conditions, not type 1. The key difference lies in how these conditions work. Type 1 diabetes is an autoimmune condition where the pancreas produces little or no insulin, whereas type 2 involves insulin resistance and impaired glucose control.
Clinical trials for Mounjaro (the SURMOUNT studies) focused on people without type 1 diabetes or those with type 2 diabetes. The medication has not been tested extensively in type 1 populations, so there is insufficient safety and efficacy data to support its use in this group. Additionally, people with type 1 diabetes already require insulin injections, and combining insulin with tirzepatide introduces complexity that requires specialist oversight.
If you have type 1 diabetes and are overweight, your GP or diabetes specialist can explore alternatives tailored to your specific situation. These may include optimising your insulin regimen, working with a dietitian, or accessing specialist weight management services through the NHS.
Clinically BackedWeight Loss
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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 Do If You Have Type 1 Diabetes and Need Weight Support
If you have type 1 diabetes and are concerned about your weight, the first step is to speak with your GP or your specialist diabetes team. They can assess your individual circumstances and recommend safe, evidence-based approaches.
In some cases, optimising your insulin management alone can support healthier weight, whilst in others a structured weight loss programme through the NHS may be appropriate. Unlike type 2 diabetes, where prescription medications like Mounjaro or Wegovy (semaglutide) may be considered, type 1 management focuses on insulin optimisation, lifestyle support, and specialist guidance.
You can use our free GLP-1 weight loss calculator and BMI calculator to track your current health metrics and discuss these with your diabetes team as part of your personalised care 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.
Is Mounjaro safe for type 1 diabetes?
Mounjaro is not approved for type 1 diabetes in the UK. It was not tested in type 1 populations during clinical trials. If you have type 1 diabetes, speak with your GP or diabetes specialist about safe, approved options for weight management tailored to your condition.
Can you take Mounjaro and insulin together?
Mounjaro is not recommended alongside insulin therapy due to lack of safety data in this combination. Type 1 diabetes requires insulin, making Mounjaro unsuitable. Your diabetes team can discuss alternatives such as optimising your insulin regimen or accessing specialist NHS weight management services.
What is the difference between type 1 and type 2 diabetes for Mounjaro eligibility?
Type 1 is an autoimmune condition; type 2 involves insulin resistance. Mounjaro is approved only for type 2 (or weight-related health conditions in non-diabetic adults). Type 1 requires insulin therapy and different management approaches, making Mounjaro unsuitable for this group.
Can I take Wegovy instead if I have type 1 diabetes?
Wegovy (semaglutide) is also not approved for type 1 diabetes. Like Mounjaro, it was tested in type 2 and non-diabetic populations. Your diabetes specialist can advise on evidence-based weight management options safe for type 1, including lifestyle support and NHS specialist services.
What alternatives are available for type 1 weight management in the UK?
Options include optimising your insulin regimen with your diabetes team, structured dietitian support, NHS tier 3 weight management services, and lifestyle programmes. Your GP can refer you to appropriate services. Discuss your specific situation to find the right approach for you.
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.