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
Taking Mounjaro For The First Time — UK Access & Cost Guide
Starting tirzepatide (Mounjaro) for the first time involves getting a prescription through either NHS specialist weight management services or private online prescribers, then learning how to self-inject weekly. This guide explains your access options in the UK, typical costs for private prescriptions, eligibility criteria, and what happens at each stage of your first appointment and injection.
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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.
How to Access Mounjaro in the UK — NHS vs Private Routes
NHS access: Mounjaro is available through NHS tier 3 specialist weight management services following NICE approval. You'll need a referral from your GP to a specialist weight management team, where a multidisciplinary assessment determines whether you're eligible. NHS access is free at point of use, but waiting lists vary significantly by region — some areas have waits of 6–18 months. Not all ICBs fund Mounjaro equally.
Private access: Available through GPhC-registered online pharmacies and private weight management clinics. You complete an online consultation with a UK-licensed prescriber who assesses your eligibility independently. No NHS referral needed. Private prescription costs typically range from £129–£320 per month depending on your dose. Starting dose (2.5 mg) is often cheaper than higher maintenance doses (15 mg). You'll pay for each 4-pen pack upfront.
What you need for private prescribing: Recent blood pressure reading, weight and height, details of any medications you take, and confirmation you're not pregnant or planning pregnancy.
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.
First Mounjaro Injection — What to Expect From Week 1
Your first injection is 2.5 mg, given as a single dose in the stomach, thigh, or upper arm — your prescriber will show you the technique. You inject once weekly at the same day/time. The KwikPen is a pre-filled auto-injection device; it takes 5–10 seconds. You'll stay on 2.5 mg for 4 weeks minimum before any dose increase. Most people experience some nausea in the first 1–2 weeks — this typically improves as your body adjusts. Eating smaller portions and avoiding fatty foods helps. Keep your injection pen refrigerated (2–8°C) until first use, then at room temperature (below 30°C) for up to 30 days after opening. Use our GLP-1 weight loss calculator to estimate your potential weight loss at different doses, and track your progress with our free progress tracker as you progress through the dose titration schedule.
- 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 much does Mounjaro cost privately in the UK?
Private Mounjaro costs typically range from £129–£320 per month, depending on your dose and provider. Starting dose (2.5 mg) is usually cheaper than higher maintenance doses. Each KwikPen contains 4 weekly doses, so you'll purchase one pen per month. Prices vary between providers, so compare quotes before committing.
Do I need NHS referral to get private Mounjaro?
No. Private online prescribers can assess your eligibility independently without an NHS referral. You complete an online consultation, provide health information, and if approved, receive a prescription sent to a GPhC-registered pharmacy. This route avoids NHS waiting lists but you pay privately.
How long are NHS Mounjaro waiting lists in the UK?
Waiting times vary significantly by region and ICB (Integrated Care Board). Some areas have waits of 6–12 months; others longer. Contact your local specialist weight management service for realistic timescales in your area. Private routes offer faster access but at personal cost.
What happens during the first online consultation for Mounjaro?
The prescriber reviews your weight, height, blood pressure, medical history, and current medications to assess whether Mounjaro is suitable. You'll be asked about pregnancy plans, allergies, and previous weight loss attempts. If approved, a prescription is issued and sent to a GPhC-registered pharmacy for dispensing.
How do I know if I'm eligible for Mounjaro?
You're typically eligible if you have a BMI of 30 kg/m² or above, or 27–29.9 with a weight-related health condition (type 2 diabetes, high blood pressure, sleep apnoea, or cardiovascular disease). A prescriber assesses your individual circumstances. Use our free BMI calculator to check your starting BMI instantly.
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.