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 Calculator — NHS and UK Information
A Mounjaro calculator helps you understand how tirzepatide (the active ingredient in Mounjaro) may support weight loss based on your current weight and health profile. This guide explains NHS eligibility criteria, NICE approved dosing, and how the UK prescription pathway works for this once-weekly injectable medicine. Whether you're considering NHS specialist services or exploring private options, understanding your individual circumstances is the first step.
10,000+ calculations today · NHS-aligned thresholds · 100% free
Calculate Your BMI Instantly
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.
NHS Eligibility and Mounjaro Dosing in the UK
In the UK, Mounjaro is available through NHS specialist tier 3 weight management services and through private prescription following clinical assessment. NICE has approved tirzepatide for use within NHS weight management pathways for eligible adults.
You may be eligible if you have:
- BMI of 30 kg/m² or above, OR
- BMI of 27–29.9 kg/m² with a weight-related health condition (type 2 diabetes, prediabetes, high blood pressure, abnormal blood fats, sleep apnoea, or history of cardiovascular disease)
For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, NHS guidelines recommend lower thresholds — eligibility may start at BMI 27.5 or above due to higher metabolic health risk at lower weights.
Standard Mounjaro doses start at 2.5 mg and escalate weekly to a maximum of 15 mg. Your GP or specialist prescriber will determine the appropriate dose based on tolerability and response. Use our free GLP-1 weight loss calculator above to explore potential weight loss outcomes at different doses based on clinical trial data.
Clinically BackedWeight Loss
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 Routes for Mounjaro in the UK
NHS access: Referral to your local tier 3 specialist weight management service (usually through your GP). NICE approval means it's an option on NHS specialist lists, though availability and waiting times vary significantly by region (ICB). Some areas have substantial waiting lists; others have limited capacity.
Private access: Available through UK-licensed prescribers via online consultations with GPhC-registered pharmacies. No NHS referral needed. Clinical assessment is still required — prescribers assess your medical history, current medications, and suitability before issuing a prescription. Use our free BMI calculator above to check your starting point, and track your progress with our progress tracker throughout your weight loss journey.
- 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 does the Mounjaro calculator work?
A Mounjaro calculator estimates potential weight loss based on your current weight and the dose you're taking, using data from SURMOUNT clinical trials. On average, participants lost 15–21% of body weight, but individual results vary significantly. It combines your baseline weight with expected percentage loss to show a range, not a assures.
What's the difference between Mounjaro and Wegovy on the NHS?
Both are GLP-1 weight loss medications licensed in the UK. Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist; Wegovy (semaglutide) is a GLP-1 agonist only. Mounjaro showed slightly higher average weight loss in trials (~20.9% vs ~14.9%), but both require prescription and clinical assessment. Availability on NHS varies.
Can I get Mounjaro through my GP directly?
Not typically as a standard GP prescription. Mounjaro access through the NHS requires referral to a specialist tier 3 weight management service. Your GP can refer you, but the specialist team assesses eligibility and prescribes. Private online prescribers can issue prescriptions without NHS referral, but a clinical assessment is still mandatory.
What weight-related health conditions qualify for Mounjaro on the NHS?
Type 2 diabetes or prediabetes, high blood pressure, abnormal blood fats (dyslipidaemia), obstructive sleep apnoea, and history of heart attack, stroke, or cardiovascular disease all qualify. You need one of these plus a BMI of 27–29.9, or a BMI of 30+ regardless of comorbidities.
How do I calculate if Mounjaro is right for me?
Use our free GLP-1 weight loss calculator to estimate potential outcomes. Then check your BMI using our free BMI calculator to see if you meet eligibility thresholds. Finally, consult your GP or a licensed prescriber for a personalised clinical assessment — they'll review your full health history, medications, and individual suitability.
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.