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 Mounjaro Called? The Generic Name & Other Names
Mounjaro is the brand name for a prescription-only weight management injection. The generic name is tirzepatide. It's manufactured by Eli Lilly and Company and is licensed for weight management in UK adults. You may also hear it referred to as the "tirzepatide KwikPen" (the injection device it comes in), but Mounjaro is the official brand name. Understanding the correct names helps when discussing this medication with your GP or prescriber.
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.
Understanding Mounjaro's Generic Name: Tirzepatide
Tirzepatide is the active ingredient in Mounjaro. It's pronounced "tir-ZEP-a-tide" and belongs to a class of medications called GIP and GLP-1 receptor agonists — a dual-mechanism approach that sets it apart from single-action weight loss injections. Tirzepatide works by activating two natural hormone pathways: GIP (glucose-dependent insulinotropic polypeptide) and GLP-1 (glucagon-like peptide-1). This dual action may help regulate appetite, reduce food cravings, and support feeling fuller after smaller meals. When you receive a prescription, it will be written as "tirzepatide" by your prescriber, but you'll collect the branded "Mounjaro KwikPen" from the pharmacy. In clinical trials (SURMOUNT-1), participants on tirzepatide lost an average of 15–21% of their body weight alongside reduced-calorie diet and increased physical activity — though individual results vary significantly. Use our free GLP-1 weight loss calculator above to explore projected results at different doses.
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.
Why Confusion Exists: Mounjaro vs. Other Names & Medications
Several other medications are available for weight management in the UK, which can create confusion. Wegovy (semaglutide) is a GLP-1 agonist licensed for weight loss — it works differently from Mounjaro's dual mechanism. Ozempic also contains semaglutide but is licensed for type 2 diabetes, not weight loss, so using it for weight management would be off-label. Understanding the differences between Mounjaro (tirzepatide), Wegovy (semaglutide), and other options helps when discussing treatment with your GP. All are prescription-only and require clinical assessment before being prescribed. Check your BMI using our free BMI calculator to understand your eligibility for prescription weight loss treatment, which typically requires a BMI of 30 or above, or 27–29 with weight-related health conditions.
- 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 tirzepatide the same as Mounjaro?
Yes. Tirzepatide is the generic name (active ingredient), and Mounjaro is the brand name. When prescribed, your doctor will write "tirzepatide" but you receive it as "Mounjaro KwikPen" from the pharmacy. Both terms refer to the same medication.
What does the KwikPen mean?
The KwikPen is simply the pre-filled injection device that delivers Mounjaro (tirzepatide). It's a convenient, colour-coded pen that holds four weekly doses. The medication inside is still tirzepatide, regardless of the device name.
Is Mounjaro the same as Ozempic?
No. Both contain different active ingredients. Mounjaro contains tirzepatide (dual GIP/GLP-1 agonist), while Ozempic contains semaglutide (GLP-1 agonist only). Ozempic is licensed for diabetes, not weight loss. Wegovy is the licensed weight loss version of semaglutide.
Why are there different names for the same medication?
Brand names (like Mounjaro) are created by pharmaceutical companies for marketing. Generic names (like tirzepatide) are the actual chemical name. Regulations require both. The KwikPen name refers to the delivery device. This is standard practice for all prescription medications in the UK.
Do I need to say "tirzepatide" or "Mounjaro" when talking to my GP?
Either is fine — your GP will understand both. Many people say "the Mounjaro injection" in conversation, but prescriptions are written as "tirzepatide." Your prescriber will be familiar with both names and the MHRA-approved medication.
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.