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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When Should I Take Mounjaro — UK Access & Cost Guide
Mounjaro (tirzepatide) is a once-weekly prescription injection for weight management in UK adults. The timing of when you can start depends on whether you access it through the NHS or privately. NHS access involves referral to specialist weight management services with potentially long waiting times, whilst private prescription routes offer faster access following an online clinical assessment. This guide explains both pathways, what eligibility looks like, and the realistic costs involved in the UK.
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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.
Private Access to Mounjaro in the UK
Private Mounjaro prescriptions are available through GPhC-registered online pharmacies following a consultation with a UK-licensed prescriber. The typical process takes 1–3 working days from consultation to receiving your first KwikPen. Costs vary by provider and dose but generally range from £129–£320 per month depending on which strength you're prescribed (doses start at 2.5 mg and escalate to a maximum of 15 mg once weekly). This route does not require NHS referral or involvement with specialist services—eligibility is assessed during your online consultation based on your BMI, medical history, and any weight-related health conditions like type 2 diabetes or high blood pressure.
- Private cost: approximately £129–£320 per month
- Access time: 1–3 working days from consultation
- No NHS referral needed
- Requires GPhC-registered pharmacy and UK-licensed prescriber
- Your prescriber will assess whether Mounjaro is suitable based on your health profile
Once prescribed, you'll receive guidance on dose titration—the process of gradually increasing your dose every 4 weeks to minimise side effects. Try our free GLP-1 weight loss calculator above to estimate potential outcomes at different doses, and use the weight converter to track your starting weight in both metric and imperial measurements.
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 — Timing & Eligibility
NHS access to Mounjaro is through tier 3 specialist weight management services. Your GP can refer you if your BMI is 30 or above (or 27+ with weight-related health conditions like type 2 diabetes). However, NHS availability varies significantly by region—some areas have waiting lists of several months or even years. NICE has approved tirzepatide for NHS use, but local ICB (Integrated Care Board) funding decisions affect actual availability. The NHS route is free at the point of use but requires patience. Private access offers faster starts but involves out-of-pocket costs. Check your local NHS options first, but if waiting times are prohibitive, private online prescription is a realistic alternative when you want to begin sooner. Use our BMI calculator above to confirm whether you meet eligibility criteria.
- 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 Mounjaro cost on the NHS in the UK?
Mounjaro is free on the NHS if prescribed through a specialist weight management service, but access varies significantly by region. Some areas have long waiting lists. Ask your GP about tier 3 weight management services in your area and expected waiting times.
Can I buy Mounjaro without an NHS referral in the UK?
Yes. Private online pharmacies offer Mounjaro prescriptions following an online clinical assessment with a UK-licensed prescriber. No NHS referral is required. Costs are typically £129–£320 per month depending on your prescribed dose.
What's the difference between Mounjaro and Wegovy for cost in the UK?
Both are available privately at similar price ranges (£129–£320 per month). Mounjaro is a dual GIP+GLP-1 agonist with doses up to 15 mg weekly. Wegovy (semaglutide) is a GLP-1 agonist with a maximum dose of 2.4 mg weekly. Clinical trial data showed Mounjaro achieved slightly higher average weight loss, but individual results vary significantly.
How long does it take to get Mounjaro privately in the UK?
Most private providers deliver within 1–3 working days of your online consultation. You'll have a video or text assessment with a prescriber, then your prescription is issued and the KwikPen is sent by courier. Some providers offer next-day delivery for an additional fee.
What do I need for an online Mounjaro prescription assessment?
You'll need to provide your BMI, height, weight, medical history, current medications, and whether you have weight-related health conditions. Some providers may also check your blood pressure or ask for blood test results. Be honest about your health—this helps the prescriber decide if Mounjaro is safe for you.
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.