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 Tirzepatide? Your UK Health Guide
Yes, Mounjaro is the brand name for tirzepatide — a prescription-only weight management injection licensed in the UK. Tirzepatide is the active ingredient that works by activating two natural hormone pathways (GIP and GLP-1) to help reduce appetite and support weight loss. It's not insulin and works differently to other weight loss medications. This guide explains what tirzepatide is, how Mounjaro works in the UK, and where to get more information about eligibility and costs.
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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 Mounjaro Tirzepatide Works
Mounjaro's active ingredient is tirzepatide, which activates two hormone receptors: GIP (glucose-dependent insulinotropic polypeptide) and GLP-1 (glucagon-like peptide-1). This dual-action mechanism is what makes tirzepatide different from other weight loss injections like Wegovy (semaglutide), which only activate the GLP-1 pathway.
When you take a Mounjaro KwikPen injection, tirzepatide may help regulate appetite, reduce food cravings, and support feeling fuller after smaller meals. It also slows gastric emptying — how quickly food leaves the stomach — though this effect typically lessens over time. Clinical trials showed that tirzepatide helped participants lose an average of 15–21% of their body weight, though individual results vary significantly. Weight loss was achieved alongside a reduced-calorie diet and increased physical activity — the medication is not a standalone treatment.
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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 Tirzepatide in the UK — Eligibility and Access
In the UK, tirzepatide is prescribed under the brand name Mounjaro. You may be eligible if you have a BMI of 30 kg/m² or above, or a BMI of 27–29.9 with weight-related health conditions like type 2 diabetes, high blood pressure, or cardiovascular disease. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, lower eligibility thresholds may apply due to higher health risks at lower BMI levels.
Check your BMI using our free BMI calculator above. Mounjaro is available through NHS specialist weight management services or private prescribing services. Access, waiting times, and costs vary significantly by region. A UK-licensed prescriber will assess whether tirzepatide is clinically appropriate for you following an online or in-person consultation.
Tirzepatide vs Other Weight Loss InjectionsMounjaro (tirzepatide) vs Wegovy (semaglutide): Both are once-weekly injections licensed in the UK for weight management, but they work differently. Tirzepatide activates two hormone pathways (GIP + GLP-1), while semaglutide activates only GLP-1. Clinical trials showed tirzepatide may produce slightly greater average weight loss (15–21%) compared to semaglutide (around 15%), though results vary between individuals. Doses, side effects, and access pathways differ — your prescriber will advise which is suitable for you based on your health profile.
Important: Ozempic also contains semaglutide, but it is NOT licensed for weight loss in the UK. Ozempic is approved only for type 2 diabetes management. Wegovy is the licensed weight management version of semaglutide.
- 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 the same as tirzepatide?
Yes. Mounjaro is the brand name for tirzepatide, the active ingredient. When your GP or prescriber mentions tirzepatide, they're referring to the medication sold as Mounjaro in the UK. Think of it like paracetamol (generic name) and Panadol (brand name) — same active ingredient, different brand.
How does tirzepatide work for weight loss?
Tirzepatide is a dual GIP and GLP-1 receptor agonist. It activates two hormone pathways that help regulate appetite, reduce food cravings, and support feeling fuller after meals. It may also slow how quickly food leaves your stomach. Clinical trials showed average weight loss of 15–21% of body weight, though results vary.
Is Mounjaro tirzepatide available on the NHS in the UK?
Yes, but access is limited. NICE has approved tirzepatide for NHS specialist tier 3/4 weight management services. You'll typically need a GP referral to a specialist service. Availability, waiting times, and eligibility vary significantly by region. Private prescription is also available through UK-licensed prescribers.
What's the difference between tirzepatide and semaglutide?
Tirzepatide (Mounjaro) activates two hormone pathways (GIP + GLP-1), while semaglutide (Wegovy) activates only GLP-1. Tirzepatide may produce slightly greater average weight loss in clinical trials. Both are once-weekly injections. Your prescriber will advise which suits your health needs.
Is tirzepatide the same as Ozempic?
No. Ozempic also contains semaglutide but is licensed only for type 2 diabetes (not weight loss) in the UK. Wegovy is the licensed weight loss version of semaglutide. Tirzepatide (Mounjaro) is a separate medication with a different mechanism — it activates two hormone pathways instead of one.
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.