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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How Long Has Mounjaro Been Used in the UK?
Mounjaro (tirzepatide) is a relatively recent addition to weight management options in the UK, with MHRA approval in the US coming in 2022 and UK MHRA approval following shortly after. Understanding when Mounjaro became available and how long it has been in clinical use helps you make informed decisions about this prescription-only medicine. While tirzepatide has been studied in clinical trials since the mid-2010s, its use for weight management in UK adults is still fairly new, making it an emerging rather than established treatment option.
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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.
Mounjaro Timeline and UK Clinical History
Tirzepatide clinical development began in research programmes from around 2014–2015, with early studies exploring how this dual GIP and GLP-1 receptor agonist could support weight management. The SURMOUNT clinical trial programme, which tested Mounjaro's effectiveness and safety, ran from 2017 to 2022 across multiple sites worldwide. In the US, the MHRA approved Mounjaro for weight management in November 2021 under the brand name Mounjaro. UK MHRA approval came shortly after in 2022, making it available for prescription through both NHS specialist weight management services and private prescribing routes. Since then, NICE has issued guidance supporting tirzepatide use within NHS tier 3 specialist services, though availability varies significantly across regions. The KwikPen device was developed specifically to make once-weekly administration straightforward for patients. Compared to other GLP-1 medications like Wegovy (semaglutide), which has been available longer, Mounjaro represents a newer dual-mechanism approach to weight management, offering a different option for eligible adults.
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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.
Accessing Mounjaro in the UK: NHS vs Private Routes
In the UK, Mounjaro access depends on your route. NHS access is through specialist tier 3 weight management services following referral from your GP — NICE guidance supports its use, but regional availability and waiting lists vary considerably. Many areas have significant delays in accessing NHS services, sometimes spanning months to over a year. Private access is faster: you complete an online consultation with a UK-licensed prescriber, and if clinically appropriate, a prescription is issued and dispensed by a GPhC-registered pharmacy. Costs typically range from £129 to £320 monthly depending on your dose. Both routes require a clinical assessment to confirm eligibility — you must have a BMI of 30 or above, or 27 or above with weight-related health conditions such as prediabetes or hypertension. Try our free GLP-1 weight loss calculator to estimate projected results at different doses before exploring your access options.
- 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.
How long has tirzepatide been used in clinical practice?
Tirzepatide has been in formal clinical trials since around 2017–2018 through the SURMOUNT programme. MHRA approval in the US came in November 2021, with UK MHRA approval following in 2022. This makes it approximately 2–3 years into clinical use in the UK as of 2025, making it newer than some alternatives.
Is Mounjaro available on the NHS in the UK?
Yes, NICE has approved tirzepatide for use within NHS specialist tier 3 weight management services. However, availability varies significantly by region (ICB), and waiting lists can be lengthy. Your GP can refer you, but access depends on your local service capacity.
How does the cost of Mounjaro compare on the NHS versus private prescription?
On the NHS, there is no direct cost if prescribed through specialist services, though waiting lists may be months long. Private prescriptions typically cost £129–£320 monthly depending on your dose. Private access is usually faster but involves upfront costs.
What's the difference between Mounjaro and Wegovy in terms of how long they've been used?
Wegovy (semaglutide) has been available longer — it was approved earlier in most markets. Mounjaro (tirzepatide) is newer but uses a dual GIP and GLP-1 mechanism. Both are prescription-only and require clinical assessment, though individual results vary with either option.
How quickly can I get Mounjaro if I go the private prescription route?
Private access is typically faster than NHS routes. Once you complete an online consultation and your prescription is approved, dispensing can happen within days. However, the clinical assessment still takes time, and availability depends on current prescriber capacity.
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.