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
Can You Inject Mounjaro Above Belly Button?
Yes, you can inject Mounjaro above your belly button. The stomach area (abdomen) is the most common injection site, and this includes the area both above and below the belly button. Mounjaro, the brand name for tirzepatide, can also be injected into your upper thigh or upper arm. This flexibility in injection sites makes the weekly KwikPen convenient for most people. Always rotate your injection site each week to help prevent skin irritation or lipodystrophy (changes to fatty tissue under the skin).
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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.
Mounjaro vs Wegovy — Injection Sites and Mechanisms Compared
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are prescription-only once-weekly injections used for weight management in UK adults, but they work through different mechanisms. Mounjaro is a dual GIP and GLP-1 receptor agonist, meaning it activates two hormone pathways, whereas Wegovy is a GLP-1 agonist only. This dual mechanism may explain why clinical trial data shows Mounjaro users experienced average weight loss of approximately 15–21% body weight in the SURMOUNT trial, compared to around 15% in the STEP trial for Wegovy at its maximum dose.
Both medications use identical injection sites: stomach (abdomen — above or below the belly button), upper thigh, or upper arm. Neither medication has special site restrictions. Individual results vary significantly, and which medication suits you best depends on your personal health circumstances, which a prescriber will assess during your clinical consultation.
- Mounjaro: 2.5–15 mg once weekly (dual GIP+GLP-1 agonist)
- Wegovy: 0.25–2.4 mg once weekly (GLP-1 agonist only)
- Both require rotation of injection sites each week
- Both available through NHS specialist services or private prescription in the UK
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.
Which Medication Is Right for You? Individual Assessment Matters
The choice between Mounjaro and Wegovy is not about injection site preference — it depends on your individual health profile, medical history, and how your body responds to treatment. Both medications require a clinical assessment by a UK-licensed prescriber before prescription. Your GP can refer you to an NHS tier 3 specialist weight management service, or you can access private prescription through an online clinical assessment. A prescriber will consider your BMI, weight-related health conditions, current medications, and contraindications to determine which is most suitable. Remember that both medications work best alongside a reduced-calorie diet and increased physical activity — medication alone is not a substitute for lifestyle changes.
- Talk to your GP or prescriber about which medication suits your health needs
- Use our GLP-1 weight loss calculator to explore potential outcomes with different approaches
- Both medications require consistent lifestyle support for best results
- 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 you inject Mounjaro anywhere on the belly above the belly button?
Yes. The entire stomach (abdominal) area above and below the belly button is an approved injection site for Mounjaro. Most people find injecting into the fatty tissue around the abdomen easiest. Always rotate your injection site each week to avoid lipodystrophy and skin irritation. If you find injecting your own stomach difficult, you can use your upper thigh or ask someone to help inject your upper arm.
Is there any difference in how Mounjaro and Wegovy work if injected in different sites?
No. The medication is absorbed subcutaneously (under the skin) regardless of which approved site you use. Injection site does not affect how either medication works — only that you rotate sites weekly. Both Mounjaro and Wegovy use identical injection site options: abdomen, upper thigh, or upper arm.
What is the main difference between Mounjaro and Wegovy for weight management?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, while Wegovy (semaglutide) activates GLP-1 only. In clinical trials, Mounjaro showed average weight loss of 15–21% body weight, compared to approximately 15% for Wegovy. However, individual results vary. Which medication is suitable depends on your personal health circumstances and a prescriber's assessment.
Do I need a prescription to get Mounjaro or Wegovy in the UK?
Yes, both are prescription-only medicines. In the UK, you can access them through an NHS specialist weight management service (tier 3) following a GP referral, or through a private online consultation with a UK-licensed prescriber. A clinical assessment is required before either medication is prescribed — neither is available over-the-counter.
Can I use our weight loss calculator to compare Mounjaro and Wegovy outcomes?
Our GLP-1 weight loss calculator can help you explore potential weight loss at different doses based on clinical trial data. However, it shows average outcomes — your individual results will vary based on your starting weight, adherence to diet and exercise, and how your body responds. A prescriber can give you more personalised guidance during your clinical assessment.
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.