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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Getting Mounjaro From Your Doctor in the UK
Mounjaro (tirzepatide) can be prescribed in the UK through both NHS specialist services and private doctors following a clinical assessment. The NHS route involves referral to tier 3 weight management services, where eligibility is assessed against NICE guidelines. Private prescribers offer an alternative pathway without NHS referral. Either way, you'll need a consultation with a qualified prescriber who will evaluate your BMI, health history, and whether Mounjaro is appropriate for you. This guide explains how the prescribing process works in the UK and what eligibility criteria apply.
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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 Mounjaro Prescribing and NICE Eligibility Criteria
NICE has approved tirzepatide (Mounjaro) for use within NHS specialist weight management services. However, NHS access is limited to tier 3 services — not standard GP prescription. Eligibility requires a BMI of 30 kg/m² or above, or a BMI of 27–29.9 with at least one weight-related health condition such as type 2 diabetes, prediabetes, high blood pressure, or cardiovascular disease. Adults of South Asian, Chinese, Black African, or Black Caribbean heritage may qualify at lower BMI thresholds (27.5 and above). Most tier 3 services now offer Mounjaro alongside other weight loss treatments. However, availability varies significantly by region — some areas have extensive waiting lists, whilst others have limited stock. Your GP can refer you, but you'll need to meet your local Integrated Care Board (ICB) criteria. Use our free BMI calculator above to check your current BMI and understand whether you may meet initial eligibility thresholds.
- BMI ≥30, or BMI 27–29.9 with weight-related comorbidity
- Referral from GP to local tier 3 service required
- Lower BMI thresholds for certain ethnic groups (27.5+)
- Assessment by specialist multidisciplinary team
- Availability varies significantly by region and ICB
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.
NHS vs Private Routes: How to Access Mounjaro in the UK
NHS route: Referral through your GP to a tier 3 weight management service. Free at point of care but subject to regional waiting lists, which can be months or even years in some areas. Prescribing follows NICE guidance strictly. Private route: Consultation with a UK-licensed prescriber through a GPhC-registered online service. Faster access (typically within days), no NHS referral needed, but you pay out of pocket — costs range from approximately £129–£320 per month depending on dose. Both routes require a clinical assessment to confirm suitability. The prescriber will review your medical history, current medications, and whether the Mounjaro KwikPen injections are appropriate for you. Track your progress once started using our free progress tracker.
- 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.
Can my GP prescribe Mounjaro directly?
Standard GPs cannot prescribe Mounjaro through the NHS. You must be referred to a tier 3 specialist weight management service by your GP. However, some GPs work with private prescribers or online services, so it's worth asking. Private doctors can prescribe directly without NHS referral.
What is the difference between NHS and private Mounjaro prescribing?
NHS prescribing is free but requires GP referral to tier 3 services and follows strict NICE eligibility criteria. Waiting lists are often very long. Private prescribing is faster and doesn't require NHS referral, but you pay out of pocket (typically £129–£320/month). Both require a proper clinical assessment.
How long are NHS waiting lists for Mounjaro?
This varies significantly by region and ICB. Some areas have 6–12 month waits, whilst others may be 18+ months or longer. Availability also depends on local stock and demand. Contact your local tier 3 service directly for the most current waiting times.
Will I need repeat prescriptions once I start Mounjaro?
Yes. Both NHS and private prescribers typically require regular follow-up appointments to monitor your progress, side effects, and dose adjustments. NHS services usually offer ongoing support through tier 3 services. Private prescribers may require periodic online consultations to issue repeat prescriptions.
What if I don't meet NHS eligibility criteria — can I get Mounjaro privately?
Yes. Private prescribers can assess you independently against their own clinical criteria, which may differ from NHS NICE guidance. However, they must still ensure the medication is clinically appropriate for you before prescribing. Individual assessment is always required.
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.