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
What Is Munjaro?
Munjaro is a prescription-only weight management injection licensed in the UK. It contains tirzepatide, a medication that works differently from other weight loss injections by activating two hormone pathways — GIP and GLP-1 receptors — rather than just one. This dual-action approach may help reduce appetite, support feeling fuller after meals, and assist with sustainable weight loss when used alongside dietary changes and increased physical activity. Clinical trials showed that Munjaro helped participants lose an average of 15–21% of their body weight, though individual results vary significantly.
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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.
How Munjaro Works
Munjaro works by activating two natural hormone pathways in your body: GIP (glucose-dependent insulinotropic polypeptide) and GLP-1 (glucagon-like peptide-1). This dual GIP and GLP-1 receptor agonist mechanism is what distinguishes it from other weight loss injections like Wegovy, which only activates the GLP-1 pathway. When you take Munjaro, it signals to your brain that you're fuller after eating smaller portions, which may reduce overall calorie intake. It also slows how quickly food leaves your stomach, giving you a prolonged feeling of fullness. The medication does not work like insulin — it helps regulate appetite and fat utilisation. You receive Munjaro as a once-weekly injection using a pre-filled KwikPen device, administered at home into your stomach, thigh, or upper arm. Doses range from 2.5 mg to 15 mg, with your prescriber increasing the dose gradually over several months based on your tolerance and response.
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 Access
In the UK, you may be eligible for Munjaro 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, prediabetes, high blood pressure, or sleep apnoea. Lower thresholds apply if you're of South Asian, Chinese, Black African, or Black Caribbean heritage, reflecting higher health risks at lower BMI levels. Munjaro is available through NHS specialist weight management services (tier 3/4) following referral from your GP, though waiting lists vary significantly by region. It's also available privately through GPhC-registered online pharmacies following a clinical assessment with a UK-licensed prescriber. Use our free BMI calculator to check whether you fall within the eligible range, and our GLP-1 weight loss calculator to estimate potential results at different doses.
- 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.
Is Munjaro the same as Ozempic?
No. Both contain semaglutide, but Ozempic is approved for type 2 diabetes (not weight loss) and Wegovy is the licensed weight management version. Munjaro contains tirzepatide, which is different — it activates both GIP and GLP-1 pathways, whereas Wegovy only activates GLP-1.
How much weight can I expect to lose on Munjaro?
Clinical trials showed average weight loss of 15–21% of body weight over 72 weeks alongside dietary changes and exercise. However, individual results vary significantly — some people lose more, others less. Your prescriber can discuss realistic expectations based on your health profile.
What are the main side effects of Munjaro?
Common side effects include nausea, diarrhoea, vomiting, and constipation — typically most noticeable when starting or increasing doses. Less common side effects include fatigue, dizziness, and injection site reactions. Serious side effects are rare but include severe stomach pain (possible pancreatitis) — seek urgent medical attention if this occurs.
How do I get Munjaro prescribed in the UK?
You can access Munjaro through NHS specialist weight management services via GP referral, or privately through an online prescriber following a clinical assessment. A licensed prescriber must confirm you're eligible based on your BMI, health history, and any weight-related conditions. Munjaro is prescription-only — you cannot buy it without a valid prescription.
Can I use Munjaro if I'm pregnant or breastfeeding?
No. Munjaro is not recommended during pregnancy or while breastfeeding. Women taking oral contraceptives should add a barrier method for 4 weeks after starting Munjaro and after each dose increase, as the medication may reduce contraceptive absorption.
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.