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
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What Is Nounjaro? A UK Health Guide
Nounjaro is the brand name for tirzepatide, a prescription-only weight management injection licensed in the UK. If you've heard about "Nounjaro" and want to understand what it is, how it works, and whether it might be relevant to you, this UK health guide covers the key facts. This information is for general educational purposes only and does not constitute medical advice. Always consult your GP or a qualified healthcare professional before making any health decisions.
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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 Nounjaro Works and What It Does
Nounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist — this means it activates two natural hormone pathways in your body that help regulate appetite and blood sugar. Unlike some other weight management injections that work through a single mechanism, Nounjaro's dual action may help reduce food cravings, support feeling fuller after smaller meals, and slow how quickly food leaves your stomach. It's injected once a week under the skin, usually in the stomach, upper thigh, or upper arm. You receive the injection yourself using a pre-filled KwikPen device. In clinical trials, Nounjaro helped participants lose an average of 15–21% of their body weight over 72 weeks — though individual results vary significantly and depend on factors including diet, physical activity, and personal metabolism. Weight loss is not assured.
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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.
UK Eligibility and How to Access Nounjaro
In the UK, Nounjaro (tirzepatide) may be prescribed for adults who have a BMI of 30 or above, or a BMI of 27–29.9 with at least one weight-related health condition such as type 2 diabetes, high blood pressure, or cardiovascular disease. Lower BMI thresholds apply for adults of South Asian, Chinese, Black African, or Black Caribbean heritage due to higher health risks at lower weights. You can access Nounjaro through NHS specialist tier 3 weight management services (via GP referral, though waiting times vary by region) or through private online prescribing following a clinical assessment with a UK-licensed prescriber. Use our free BMI calculator to check your personal BMI instantly, and our GLP-1 weight loss calculator to estimate potential outcomes 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 Nounjaro the same as Mounjaro?
Yes — Nounjaro and Mounjaro are the same medication (tirzepatide). "Nounjaro" is an alternative spelling sometimes used colloquially, but the official brand name is Mounjaro. Both refer to the same prescription injection manufactured by Eli Lilly for weight management in the UK.
How is Nounjaro different from Wegovy?
Nounjaro (tirzepatide) is a dual GIP and GLP-1 agonist, while Wegovy (semaglutide) is a GLP-1 agonist only. In clinical trials, Nounjaro showed slightly higher average weight loss (up to 21% vs 15% for Wegovy), though both are effective. Individual results vary, and the right choice depends on personal health factors and clinical assessment.
What are the main side effects of Nounjaro?
Common side effects include nausea, diarrhoea, vomiting, constipation, and stomach pain — particularly when starting or increasing doses. Most side effects improve over time. Serious but rare side effects include severe stomach pain (possible pancreatitis) and gallbladder problems. Always report persistent symptoms to your prescriber.
How much does Nounjaro cost in the UK?
On the NHS, Nounjaro is available through specialist weight management services at no direct cost. Privately, costs vary by provider and dose, typically ranging from £130–£320 per month. Prices depend on which dose you're prescribed and your chosen pharmacy.
Can I get Nounjaro from my GP?
Most GPs cannot prescribe Nounjaro directly. NHS access is through specialist tier 3 weight management services — your GP can refer you, but you'll need assessment and ongoing monitoring by specialist clinicians. Private prescriptions are available online after assessment with a UK-licensed prescriber.
Ready to take control of your weight loss journey?
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