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
When Did Mounjaro Come Out in the UK?
Mounjaro (tirzepatide) was approved for weight management in the UK by the MHRA in November 2023, making it available through private prescribing shortly after. NHS prescribing guidance through NICE came later in 2024, enabling access through specialist weight management services. This timeline matters if you're considering tirzepatide as a weight loss option—understanding when it became available helps explain current access routes and waiting times across the UK.
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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 UK Approval and NHS Timeline
Mounjaro received MHRA (Medicines and Healthcare products Regulatory Agency) approval in November 2023, initially making it available through private prescribing channels. This was ahead of many European countries. By mid-2024, NICE (National Institute for Health and Care Excellence) published guidance recommending tirzepatide for use within NHS specialist weight management services, subject to ICB (Integrated Care Board) commissioning decisions.
The Mounjaro KwikPen—the pre-filled injection device—has been available in the UK since approval, administered once weekly at doses from 2.5 mg to 15 mg. Access through NHS tier 3 specialist services began rolling out in 2024, though availability varies significantly by region. Private prescribing became available immediately after MHRA approval, making Mounjaro accessible without NHS waiting lists for those able to afford it.
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No appointments. No waiting rooms. Just care — from a UK-regulated online pharmacy.
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.
NHS vs Private Access for Mounjaro in the UK
NHS access requires referral to a specialist weight management service from your GP. Once referred, you'll be assessed for eligibility based on BMI and weight-related health conditions. However, NHS waiting times remain substantial in many regions—some areas have lists extending to many months.
Private access became available immediately following MHRA approval in 2023. A UK-licensed prescriber assesses your suitability online, and if approved, your prescription is dispensed by a GPhC-registered pharmacy. This route doesn't require an NHS referral. Our GLP-1 weight loss calculator can help you estimate potential outcomes at different Mounjaro doses. Use our BMI calculator to check your current weight category and eligibility criteria.
- 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.
What is tirzepatide, and how is it different from semaglutide?
Tirzepatide (Mounjaro) is a dual GIP and GLP-1 receptor agonist, meaning it activates two natural hormone pathways. Semaglutide (Wegovy) is a GLP-1 agonist only, activating one pathway. Clinical trials suggest tirzepatide may produce slightly greater average weight loss, though individual results vary significantly. Both are prescription-only once-weekly injections.
Was Mounjaro available on the NHS when it first came out?
No. When Mounjaro received MHRA approval in November 2023, it was only available privately. NHS prescribing through specialist services began in 2024 after NICE published guidance. Your GP can refer you to a tier 3 specialist weight management service for assessment, but availability depends on your local ICB commissioning.
How does Mounjaro KwikPen work?
The Mounjaro KwikPen is a pre-filled, single-use pen device injected once weekly. You self-inject into your abdomen, thigh, or upper arm (with assistance). Each pen contains one dose. Storage requires refrigeration when unopened (2–8°C), though it can be kept at room temperature below 30°C for up to 30 days after first use.
Am I eligible for Mounjaro on the NHS?
NHS eligibility typically requires a BMI of 30 kg/m² or above, or 27–29.9 with weight-related health conditions like type 2 diabetes, high blood pressure, or cardiovascular disease. For South Asian, Chinese, Black African, or Black Caribbean adults, lower thresholds may apply. Your GP or specialist will assess your individual circumstances.
What's the difference between NHS and private Mounjaro access?
NHS access requires a GP referral to specialist services—free but with waiting lists. Private access is available immediately following an online assessment—not free, but faster. Both routes require clinical assessment and a valid prescription. Individual results with Mounjaro vary, and use alongside a reduced-calorie diet is recommended.
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.