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
Who Can Prescribe Mounjaro in the UK?
In the UK, Mounjaro (tirzepatide) is a prescription-only medicine, so it can only be prescribed by qualified, licensed healthcare professionals following a clinical assessment. This includes NHS specialists through tier 3 weight management services, private doctors, and registered online prescribers. The prescriber will check your eligibility based on your BMI, health conditions, and medical history before issuing a Mounjaro KwikPen prescription. You cannot buy Mounjaro without a valid prescription from a licensed practitioner.
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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 vs Private Prescribing Routes
NHS Route: Mounjaro is available through NHS specialist weight management services (tier 3). You'll need a referral from your GP to access these services. NICE has approved tirzepatide for use within the NHS, but availability varies significantly by region and local commissioning. Some areas have extensive waiting lists. The prescriber will assess your BMI (30 or above, or 27–29.9 with weight-related conditions) and manage your Mounjaro dose titration over time.
Private Route: Licensed private doctors and registered online prescribing services can issue Mounjaro prescriptions without NHS referral. An online clinical assessment replaces the face-to-face appointment. The prescription is then dispensed by a GPhC-registered pharmacy. Private prescribing typically offers faster access than NHS waiting lists, though at a cost of approximately £129–£320 per month depending on dose.
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.
Eligibility Checks & Next Steps
Any prescriber—NHS or private—will assess whether Mounjaro is suitable by reviewing your BMI, weight-related health conditions (such as type 2 diabetes, high blood pressure, or sleep apnoea), medical history, and current medications. You cannot receive Mounjaro if you're pregnant, breastfeeding, under 18, or have contraindications like personal or family history of thyroid cancer. Compared to Wegovy, Mounjaro has a dual GIP/GLP-1 mechanism and may offer different outcomes—your prescriber will discuss which option suits you. To start: contact your GP for NHS referral, or book an online consultation with a private prescriber. Always ensure they're UK-licensed before proceeding.
- 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.
Can my GP prescribe Mounjaro directly?
Not typically. Standard GPs cannot prescribe Mounjaro on the NHS. You need a referral to a tier 3 specialist weight management service, where trained weight management doctors will assess and prescribe if you're eligible. Some private GPs can prescribe it outside the NHS following their own clinical assessment.
How do online Mounjaro prescribers work in the UK?
Online prescribers are UK-licensed doctors registered with the General Medical Council (GMC). You complete an online health questionnaire and video consultation. If eligible, they issue a prescription to a GPhC-registered pharmacy, which dispenses your Mounjaro KwikPen. This bypasses NHS waiting lists but requires payment.
What will a prescriber ask me?
They'll check your current weight and BMI, any weight-related conditions (diabetes, hypertension, sleep apnoea), allergies, current medications, pregnancy status, and medical history. They may ask about lifestyle and previous weight loss attempts. This ensures Mounjaro is safe and appropriate for you.
Is Mounjaro available on the NHS in all areas?
No. NICE has approved tirzepatide, but NHS availability depends on your local Integrated Care Board (ICB) funding and commissioning decisions. Some areas offer it readily; others have long waiting lists or limited access. Contact your local NHS weight management service to check availability in your region.
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.