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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Best Mounjaro Injection Site — Where to Inject and How to Access
If you're considering Mounjaro as a weekly weight loss injection in the UK, knowing where and how to inject it safely is essential — as is understanding your access options and costs. Mounjaro (tirzepatide) is a prescription-only medicine available through both NHS specialist services and private online consultations. This guide covers the approved injection sites, what to expect during dose titration, and the realistic cost differences between NHS and private routes in 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.
Where to Inject Mounjaro Safely
Mounjaro comes as a pre-filled KwikPen device and can be injected into three approved body sites: your stomach (abdomen), upper thigh, or upper arm.
- Stomach (abdomen): Most common site. Inject 5cm (2 inches) away from the belly button, avoiding any scars or areas of redness.
- Upper thigh: Outer side of the thigh, halfway between hip and knee. Suitable for self-injection.
- Upper arm: Back of the arm, between shoulder and elbow. Typically requires assistance from another person.
Rotate your injection site each week to prevent skin reactions or lipohypertrophy (fatty bumps). Use a fresh needle for each injection and allow the pen to reach room temperature before injecting. Store unopened pens in the fridge at 2–8°C; once opened, you can keep a pen at room temperature (below 30°C) for up to 30 days.
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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.
Mounjaro Cost and Access in the UK
NHS route: Access is through specialist tier 3 weight management services. Your GP refers you, and a specialist team assesses your eligibility (usually BMI ≥30 or BMI ≥27 with weight-related health conditions). NHS availability varies significantly by region, and waiting lists can be lengthy.
Private route: You can obtain a prescription through a private online consultation with a UK-licensed prescriber. Costs typically range from £129–£320 per month depending on your dose. A 5mg dose costs less than the maximum 15mg dose. No NHS referral needed — you proceed directly to prescription and dispensing by a registered pharmacy, making this a faster access route for those who can afford private costs.
- 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 are the approved Mounjaro injection sites in the UK?
The three approved injection sites are your stomach (abdomen), upper thigh, and upper arm. Rotate sites each week to avoid skin reactions. Stomach injection is most common, while the upper arm typically requires help from another person.
How much does Mounjaro cost privately in the UK?
Private Mounjaro costs typically range from £129–£320 per month depending on your dose. Lower doses (2.5–5mg) cost less than higher maintenance doses (10–15mg). Prices vary between private prescribers and pharmacies, so it's worth comparing.
Can I get Mounjaro free on the NHS in the UK?
Yes, but access is through specialist tier 3 weight management services. Your GP must refer you, and a specialist team assesses whether you meet eligibility criteria. NHS availability and waiting times vary considerably by region. Contact your local ICB (integrated care board) for current availability.
How do I get Mounjaro on prescription privately?
You complete an online health questionnaire with a UK-licensed prescriber. They assess your BMI, weight-related health conditions, and medications. If approved, a prescription is issued to a registered pharmacy. The process typically takes a few days from consultation to prescription.
Do I need to see my GP before starting Mounjaro privately?
Not necessarily. You can consult a private prescriber directly without a GP referral. However, it's good practice to inform your GP, especially if you take other medications, as Mounjaro may affect absorption of some oral medicines like contraceptives.
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.