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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Weight Support with Mounjaro
Mounjaro (tirzepatide) is a prescription-only weekly weight loss injection that works by activating two natural hormone pathways to support appetite control and weight management. In the UK, it's available through NHS specialist services or private prescribing following clinical assessment. This guide explains how Mounjaro supports weight, who may be eligible, and what to expect. Use our free GLP-1 weight loss calculator above to estimate potential weight loss outcomes at different doses.
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.
How Mounjaro Supports Weight Management
Mounjaro is a dual GIP and GLP-1 receptor agonist — meaning it works on two hormone pathways in the body. This dual mechanism sets it apart from other weight loss injections like Wegovy (semaglutide), which targets only GLP-1. The medication helps support weight by:
- Reducing appetite and food cravings
- Helping you feel fuller after smaller meals
- Slowing how quickly food leaves the stomach
- Supporting natural appetite regulation signals to the brain
In clinical trials (SURMOUNT-1), participants using Mounjaro as a weekly weight loss injection alongside a reduced-calorie diet and increased physical activity achieved average weight loss of 15–21% of body weight over 72 weeks — though individual results vary significantly. Mounjaro is injected once weekly using a pre-filled KwikPen device. It is not insulin and does not work like insulin.
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.
UK Eligibility and How to Access Mounjaro
You may be eligible for Mounjaro in the UK if you have a BMI of 30 or above, or a BMI of 27–29.9 with weight-related health conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, lower thresholds may apply. Access is available through NHS specialist tier 3 weight management services (via GP referral, though waiting lists vary by region) or through private prescribing with a UK-licensed prescriber following online clinical assessment. Your GP or prescriber will assess whether Mounjaro is suitable based on your individual health and medical history. Calculate your BMI instantly with our free BMI calculator to see where you stand.
- 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 weight can I expect to lose with Mounjaro?
Clinical trials showed an average weight loss of 15–21% of body weight over 72 weeks on maximum dose, alongside diet and exercise. However, individual results vary — some people lose more, some less. Weight loss is not assured and depends on your starting weight, lifestyle changes, and how your body responds to the medication.
Is Mounjaro the same as Wegovy?
No. Both are prescription-only weight loss injections, but they work differently. Mounjaro (tirzepatide) activates two hormone pathways (GIP + GLP-1), while Wegovy (semaglutide) targets only GLP-1. Clinical trials suggest Mounjaro may support slightly greater average weight loss, but the difference is modest and individual results vary.
How do I get Mounjaro on the NHS in the UK?
Ask your GP for referral to your local NHS tier 3 specialist weight management service. NICE has approved tirzepatide for NHS use, but access varies by region and availability can be limited. Waiting lists for NHS specialist services can be several months. Private prescription is also available if NHS access is limited in your area.
What is the starting dose of Mounjaro?
The starting dose is 2.5 mg once weekly for 4 weeks, then typically increased to 5 mg. Your prescriber may increase further based on your response and tolerance, up to a maximum of 15 mg weekly. Dose adjustments happen over weeks, not days.
Does Mounjaro require a prescription in the UK?
Yes, Mounjaro is prescription-only. You cannot buy it without a valid prescription from a UK-licensed prescriber. Any prescription must follow a clinical assessment to ensure it's safe and appropriate for your individual health profile and medical history.
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.