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
Is Mounjaro a Supplement?
Mounjaro is not a supplement — it's a prescription-only weight management injection licensed for use in the UK. Made by Eli Lilly, Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist that works differently from vitamins or dietary supplements. It requires a prescription from a UK-licensed healthcare professional and a clinical assessment to determine eligibility. Understanding what Mounjaro actually is helps you make informed decisions about weight management options available to you.
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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.
What Makes Mounjaro Different From Supplements
Unlike over-the-counter supplements, Mounjaro is a regulated pharmaceutical medicine subject to MHRA approval and monitoring. Supplements contain vitamins, minerals, or herbal extracts; Mounjaro is a synthetic injectable medication that mimics natural hormones your body produces. It activates two distinct hormone pathways — GIP (glucose-dependent insulinotropic polypeptide) and GLP-1 (glucagon-like peptide-1) — to help regulate appetite and support weight loss alongside reduced-calorie diet and increased physical activity.
Mounjaro comes as a pre-filled KwikPen device for once-weekly injections at doses ranging from 2.5 mg to 15 mg. You must be assessed by a prescriber who will check your medical history, current medications, and eligibility before issuing a prescription. This clinical assessment is mandatory — unlike supplements, which you can purchase without professional oversight.
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 Prescription Requirements and Eligibility
To access Mounjaro in the UK, you must have a BMI of 30 kg/m² or above, or BMI of 27–29.9 kg/m² with at least one weight-related health condition such as type 2 diabetes, high blood pressure, or cardiovascular disease. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds may apply. You can use our free BMI calculator above to check your personal BMI instantly.
Mounjaro is available through NHS specialist weight management services (tier 3/4) or private online prescribing services. NHS access typically requires GP referral and may involve waiting lists. Private prescribers offer faster access following an online clinical assessment. Either route requires a licensed UK prescriber to authorise the prescription.
How Mounjaro Works as a Weight Management MedicineMounjaro's dual mechanism sets it apart from single-action alternatives like Wegovy (semaglutide). By activating both GIP and GLP-1 pathways, Mounjaro may help reduce appetite more effectively, support feeling fuller after smaller meals, and slow gastric emptying. Clinical trial data showed participants lost an average of 15–21% of their body weight over 72 weeks — though individual results vary significantly and depend on dose, adherence, diet, and physical activity.
Try our GLP-1 weight loss calculator to see projected weight loss outcomes at different doses. Weight loss is not assured, and Mounjaro is most effective when combined with lifestyle changes rather than used alone.
- 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 Mounjaro a vitamin or supplement?
No. Mounjaro is a prescription-only pharmaceutical medicine, not a supplement. It's a synthetic injectable medication (tirzepatide) that requires clinical assessment and a prescription from a UK-licensed healthcare professional. Supplements don't need prescriptions; Mounjaro does.
Can I buy Mounjaro over the counter like a supplement?
No, Mounjaro is prescription-only in the UK and cannot be purchased without a prescription. You must be assessed by a prescriber (NHS or private) who will confirm you're eligible based on BMI and health conditions before issuing a prescription.
How is Mounjaro different from weight loss supplements?
Mounjaro is a regulated pharmaceutical medicine approved by the MHRA. Unlike supplements, it's subject to rigorous safety monitoring and has clinical trial evidence supporting its effectiveness. It's a synthetic injectable hormone agonist, not an herbal extract or vitamin.
What's the difference between Mounjaro and Wegovy?
Both are prescription weight loss injections available in the UK. Mounjaro (tirzepatide) is a dual GIP+GLP-1 agonist; Wegovy (semaglutide) activates GLP-1 only. Mounjaro showed slightly higher average weight loss in trials (~20.9% vs ~14.9%), though individual results vary. Your prescriber will assess which is suitable.
Do I need NHS approval or a GP referral to get Mounjaro?
For NHS access, you typically need a GP referral to specialist tier 3 weight management services. Private prescribers offer an alternative route — you can access online consultations directly without NHS referral. Either way, a licensed UK prescriber must assess and authorise your prescription.
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.