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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Tirzepatide Reviews — What the Evidence Shows
Tirzepatide, sold as Mounjaro in the UK, is a prescription-only weight management injection that has generated significant interest since its approval. If you're researching tirzepatide reviews and real-world experiences, you'll want to understand both the clinical evidence and what users report. This guide covers what the trials showed, common feedback themes, and how tirzepatide compares to other options like semaglutide. We'll help you understand whether this GLP-1 and GIP receptor agonist might be suitable for you and how to access it through the NHS or privately.
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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 Clinical Trials Showed About Tirzepatide
The SURMOUNT-1 clinical trial, the primary evidence for tirzepatide's weight loss effect, followed adults over 72 weeks. At the maximum dose of 15 mg weekly, participants lost an average of approximately 20.9% of their body weight — though individual results varied significantly. At 10 mg, average loss was around 19.5%, and at the lower 5 mg dose, approximately 15%. These results were achieved alongside a reduced-calorie diet and increased physical activity, not by the injection alone.
Important context: these are clinical trial averages. Real-world reviews show that some users lose more, others less, and a small percentage experience minimal weight loss. The weekly weight loss injection mechanism works by activating both GIP and GLP-1 receptors — a dual action that differs from single GLP-1 medications like semaglutide (Wegovy). Side effects in trials were common but usually manageable, with nausea, constipation, and diarrhoea being most frequent, typically reducing over time as the body adjusts.
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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.
What Users Report — Common Themes from Reviews
Across real-world reviews and user feedback, several themes emerge consistently. Many users report reduced appetite and food cravings within the first few weeks, describing it as "naturally eating less" rather than forcing restriction. Energy levels vary — some report improved energy, others note fatigue, particularly during dose escalation. Side effects tend to be most noticeable in weeks 1–4 of each dose increase, then improve. Users often highlight the convenience of once-weekly dosing via the Mounjaro KwikPen compared to daily injections.
Cost is a significant theme in UK reviews — private treatment ranges from £129–£320 monthly depending on dose, whilst NHS access through specialist services is free but involves longer waiting lists. Weight loss plateaus are commonly reported around weeks 12–16, then often resume with continued treatment. Users emphasise that results depend heavily on diet and activity; the injection supports but doesn't replace lifestyle effort.
- 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 active ingredient; Mounjaro is the brand name. It's a prescription-only GLP-1 and GIP receptor agonist injection licensed in the UK for weight management in adults with a BMI of 30 or above, or 27–29.9 with weight-related health conditions.
How long before tirzepatide reviews show real weight loss?
Most users report noticeable appetite reduction within 1–2 weeks, but measurable weight loss typically appears by week 4–6. Use our GLP-1 weight loss calculator to estimate potential loss at different doses based on clinical trial data.
Does tirzepatide work better than semaglutide (Wegovy)?
Clinical trials suggest tirzepatide may produce slightly greater average weight loss (20.9% vs 14.9%) due to its dual GIP+GLP-1 mechanism versus semaglutide's single GLP-1 action. However, individual results vary significantly. Your GP or prescriber can advise which is more suitable for you.
Can I get tirzepatide reviews from real NHS patients?
NHS access to tirzepatide is limited and varies by region through specialist tier 3 weight management services. Private online prescribing allows broader access following clinical assessment. Real-world reviews are available online, but always verify information with your GP before starting treatment.
What makes tirzepatide reviews mention fewer side effects over time?
Most side effects (nausea, diarrhoea, constipation) appear during dose escalation then diminish within 1–2 weeks as your body adjusts. Staying hydrated, eating smaller meals, and taking time between doses all help. However, if side effects persist, inform your prescriber — dose adjustments are possible.
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.