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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How to Get Mounjaro From Your Doctor in the UK
If you're considering Mounjaro (tirzepatide) for weight management in the UK, your GP is your first point of contact. However, getting this prescription medicine isn't as straightforward as a standard GP prescription. Mounjaro is typically prescribed through specialist NHS tier 3 weight management services, though private prescribing is also available. Understanding how NHS and private routes work, what your doctor will assess, and whether you meet NICE eligibility criteria will help you have an informed conversation with your healthcare team about whether this medication 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.
NHS Eligibility and How Mounjaro Prescribing Works
In the UK, Mounjaro (tirzepatide) is approved for weight management but prescribing is primarily through specialist services, not routine GP practices. NICE has approved tirzepatide for use within NHS specialist tier 3 and tier 4 weight management services, meaning your GP will typically refer you to a local specialist weight management clinic rather than prescribe directly.
Your GP can assess whether you meet NHS eligibility criteria. You may qualify if you have:
- A BMI of 30 kg/m² or above, or BMI 27–29.9 with at least one weight-related health condition (such as type 2 diabetes, prediabetes, high blood pressure, sleep apnoea, or cardiovascular disease)
- For South Asian, Chinese, Black African, or Black Caribbean adults: lower BMI thresholds may apply (eligibility from BMI 27.5 or above)
- Demonstrated commitment to lifestyle changes including diet and physical activity
Your doctor will also check that you have no contraindications, such as pregnancy, personal or family history of medullary thyroid cancer, or multiple endocrine neoplasia (MEN2). Access through NHS specialist services varies significantly by region — some areas have lengthy waiting lists, while others may have limited availability.
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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
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NHS vs Private Routes — What Your Doctor Needs to Know
If NHS waiting lists in your area are long or unavailable, private prescribing is an alternative. Private prescribers can issue Mounjaro prescriptions following a detailed online clinical assessment, and the medication is dispensed by a GPhC-registered pharmacy. Your GP doesn't need to be involved in the private route, though it's good practice to inform them you're starting any new medication.
Whether NHS or private, your doctor (or private prescriber) will evaluate your medical history, current medications, and weight loss goals. They'll discuss how Mounjaro works as a dual GIP and GLP-1 agonist, explain potential side effects such as nausea and gastrointestinal changes, and emphasise that medication works best alongside a reduced-calorie diet and increased physical activity. Use the BMI calculator on this page to check your starting point, and our GLP-1 weight loss calculator to explore projected outcomes at different doses of tirzepatide.
- 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.
Will my GP prescribe Mounjaro directly?
Most GPs do not prescribe Mounjaro directly. Instead, they refer eligible patients to NHS specialist tier 3 weight management services. However, some integrated care boards (ICBs) have different arrangements — ask your GP about the pathway in your local area. Private prescribing bypasses NHS referral.
What will my doctor ask me during a Mounjaro consultation?
Your doctor will review your medical history, current medications, BMI, weight-related health conditions, and previous weight loss attempts. They'll discuss your expectations, confirm you understand the need for lifestyle changes, and check for contraindications such as pregnancy or personal/family history of medullary thyroid cancer.
How long does it take to get Mounjaro through the NHS?
NHS waiting times vary considerably by region. Some specialist weight management services have waiting lists of several months to over a year. Private routes are typically faster, with prescriptions often issued within 1–2 weeks of assessment. Your GP can advise on local NHS availability.
What if my doctor says I'm not eligible for Mounjaro?
If you don't meet NHS criteria or your GP refers you but tier 3 services decline, you can explore private prescribing options. A private prescriber will conduct an independent clinical assessment. However, your GP's input about your medical history is always valuable — ask them to explain which criteria you don't meet.
Can my doctor switch me from Wegovy to Mounjaro?
Yes, your doctor (NHS or private) can consider switching between GLP-1 medications. Mounjaro has a dual mechanism (GIP + GLP-1) versus Wegovy's single GLP-1 action, which may suit some patients better. Any switch should be managed by your prescriber — never stop and start medications independently.
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.