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 Tirzepatide Safe in the UK?
Tirzepatide, marketed as Mounjaro, is a prescription-only GLP-1 receptor agonist approved by the MHRA for weight management in UK adults. Safety data from clinical trials and NHS guidance confirm it can be effective when prescribed appropriately, though like all medicines, it carries potential side effects. Understanding how to access tirzepatide safely through NHS or private prescription routes, along with the associated costs, helps you make an informed decision about whether this weekly weight loss injection is right for 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.
Tirzepatide Safety Profile and Clinical Evidence
Tirzepatide has been extensively studied in clinical trials, with safety data informing MHRA approval and ongoing NHS use. The GIP receptor agonist component works alongside the GLP-1 pathway to regulate appetite and support weight management. In the SURMOUNT clinical trials, the most common side effects were gastrointestinal—nausea, diarrhoea, vomiting, and constipation—which typically improve as your body adjusts to the medication.
- Very common side effects: nausea, diarrhoea, vomiting, stomach pain
- Common side effects: indigestion, fatigue, dizziness, injection site reactions, hair loss
- Serious but rare: pancreatitis, severe allergic reactions, gallbladder problems
Tirzepatide is not suitable for everyone—pregnancy, breastfeeding, and certain medical conditions exclude use. Your prescriber will assess your individual health before issuing a prescription, ensuring safety through proper clinical evaluation.
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 Cost and Access Routes for Tirzepatide
In the UK, accessing tirzepatide depends on your eligibility and preferred route. NHS access is through specialist tier 3 or 4 weight management services—typically requiring GP referral and meeting BMI thresholds (usually BMI 30+, or 27+ with weight-related health conditions). NHS waiting lists can be lengthy in many regions, sometimes extending several months.
Private prescription access is faster: online consultations with UK-licensed prescribers cost £0–£150, and private prescriptions are dispensed by GPhC-registered pharmacies. Tirzepatide costs approximately £129–£320 per month depending on dose (starting 2.5mg, increasing to 15mg maximum), making it an ongoing financial commitment. Many people track their progress using our free weight loss calculator to monitor outcomes across 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.
How much does tirzepatide cost in the UK privately?
Private tirzepatide typically costs £129–£320 per month depending on the dose. Starting doses (2.5mg) are usually cheaper; maximum maintenance doses (15mg) cost more. Costs vary by provider, and you'll also need to factor in the initial online consultation fee (£0–£150) and repeat consultations for dose adjustments.
Can I get tirzepatide on the NHS in the UK?
Yes, tirzepatide is available through NHS specialist weight management services (tier 3 and 4). You'll need GP referral and must meet eligibility criteria (typically BMI 30+). However, NHS availability varies significantly by region, and waiting lists can be several months long in many areas.
Is tirzepatide the same as Mounjaro?
Yes—tirzepatide is the active ingredient; Mounjaro is the brand name under which it's prescribed in the UK. It comes as a once-weekly injection in a KwikPen device. The weekly injection format makes it distinct from daily alternatives like liraglutide (Saxenda).
What medical assessment is needed before tirzepatide?
A UK-licensed prescriber will review your medical history, BMI, weight-related health conditions, medications, and contraindications (pregnancy, breastfeeding, pancreatitis history, etc.). This assessment happens via online consultation on the private route or through NHS specialist services, ensuring tirzepatide is safe for you personally.
How do I know if tirzepatide is working?
Track weight loss using our free BMI calculator and progress tracker—clinical trials showed an average 15–clinically studied weight loss with tirzepatide, though individual results vary. You'll also notice appetite changes within the first few weeks. Your prescriber will monitor your response at follow-up consultations.
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.