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 currently approved or recommended for people with type 1 diabetes in the UK, despite being licensed for weight management in adults. If you have type 1 diabetes and are concerned about weight management, your GP or diabetes specialist can discuss safe alternatives tailored to your individual health needs. This guide explains why Mounjaro is not suitable for type 1 diabetes, what the evidence shows, and what options may be available to you through the NHS.
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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 Used in Type 1 Diabetes
Mounjaro is a dual GIP and GLP-1 receptor agonist — it activates two natural hormone pathways to help regulate appetite and blood sugar. However, it is not licensed or recommended for type 1 diabetes in the UK or internationally.
Type 1 diabetes is an autoimmune condition where the pancreas produces little or no insulin. Managing it requires careful insulin therapy and carbohydrate counting. Mounjaro was not studied in type 1 diabetes populations, and there is no evidence from clinical trials showing it is safe or effective for this condition. The SURMOUNT trials (which established Mounjaro's weight loss benefits) excluded people with type 1 diabetes. Additionally, combining Mounjaro with insulin therapy could increase the risk of low blood sugar (hypoglycaemia) without proper specialist monitoring. Your diabetes specialist or GP will not prescribe Mounjaro if you have type 1 diabetes.
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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 Your GP or Diabetes Team Can Offer Instead
If you have type 1 diabetes and are struggling with weight management, speak to your diabetes team or GP about safe alternatives. Structured weight loss programmes, referral to a specialist dietitian, and optimised insulin regimens may all help. In some cases, GLP-1 medications originally designed for type 2 diabetes (such as Saxenda or semaglutide) have been studied in type 1 diabetes and may be considered by specialists in specialist diabetes centres — but this would only happen following detailed assessment and specialist consultation. NHS tier 3 specialist weight management services can also discuss tailored approaches. Your diabetes control and medication safety must always come first, so personalised advice from your diabetes team is essential.
- 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?
No. Mounjaro is not approved for type 1 diabetes in the UK. It was not studied in type 1 diabetes populations, and there is no safety or efficacy evidence. Combined with insulin, it could increase hypoglycaemia risk. Your diabetes specialist will not prescribe it for type 1 diabetes.
Can I use Wegovy or Saxenda instead if I have type 1 diabetes?
Saxenda (liraglutide) is also not licensed for type 1 diabetes. However, some GLP-1 medications have been studied in type 1 diabetes research settings. Any consideration would require referral to a specialist diabetes centre. Always consult your diabetes team before considering any weight loss medication.
What should I do if I have type 1 diabetes and need weight management support?
Speak to your GP or diabetes specialist. Options include referral to a specialist dietitian, structured weight loss programmes, optimisation of your insulin regimen, and referral to NHS tier 3 weight management services. Your diabetes control is the priority.
Why wasn't Mounjaro tested in type 1 diabetes?
The SURMOUNT clinical trials deliberately excluded people with type 1 diabetes to isolate its effects in other populations. Tirzepatide development focused on type 2 diabetes and weight management in non-type-1 populations. Safety in type 1 remains unknown.
Could my diabetes specialist prescribe Mounjaro off-label for weight loss?
Very unlikely. Off-label prescribing of Mounjaro in type 1 diabetes carries unknown risks, especially with insulin co-therapy. Specialist diabetes centres have safer, evidence-based approaches. Always discuss weight concerns with your diabetes team rather than seeking off-label options.
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.