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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Weight Gain on Mounjaro — How to Access It in the UK
If you're considering Mounjaro (tirzepatide) for weight management in the UK, understanding how to access it and what it costs is essential. Some people experience weight gain between doses or after stopping treatment, which is why consistent access and proper dose titration matter. This guide covers both NHS and private routes to prescription weight loss medication, helping you understand your options and what to expect during the online consultation process.
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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 Prescription Costs and UK Access Routes
Private access to Mounjaro is available through GPhC-registered online pharmacies following a clinical assessment from a UK-licensed prescriber. Costs typically range from £129 to £320 per month depending on your dose, as Mounjaro comes in different strengths requiring dose titration over time. Each KwikPen contains 4 weekly injections, so you'll need a fresh pen each month. The weekly weight loss injection format means consistent dosing is possible without NHS waiting lists.
- Starting dose (2.5 mg): usually lower cost, £129–£180/month
- Maintenance doses (5–15 mg): £180–£320/month depending on strength
- Private prescribers assess your BMI, health conditions, and medications before issuing a prescription
- No NHS referral needed — available to anyone meeting clinical criteria
- Treatment continues as long as you're prescribed and paying for it
Costs vary between providers, so it's worth comparing. Most private providers offer a consultation fee (typically £20–£50) that may be offset against your first prescription.
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 Access and What to Expect
NHS access to Mounjaro is through tier 3 specialist weight management services, typically following referral from your GP. However, NHS availability is limited — waiting lists can be months or years in many regions, and not all ICBs currently commission tirzepatide. NICE has approved Mounjaro for NHS use, but actual availability depends on your local area.
Private online consultation is faster: you'll complete a health questionnaire, have a video or phone assessment with a prescriber, and receive your prescription within 24–48 hours if approved. You'll need to provide details about your weight, height, blood pressure, medical history, and current medications. The prescriber assesses whether Mounjaro is suitable — contraindications include pregnancy, certain medications, and severe gastroparesis. Once prescribed, your medication is dispatched by post.
Use our free BMI calculator above to confirm your starting point — you'll likely need a BMI of 30 or above (or 27+ with weight-related health conditions) to be eligible. Our GLP-1 weight loss calculator can help you estimate potential outcomes at different doses. Track your progress using our free progress tracker once you start treatment, monitoring both weight and how you feel at each dose level.
- 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.
Does weight gain happen on Mounjaro, and why?
Weight gain on Mounjaro is uncommon but can happen if doses are too low, you miss injections, or you return to pre-treatment eating habits. Appetite suppression from GLP-1 activation is dose-dependent — lower doses (2.5–5 mg) have less effect than higher doses (10–15 mg). Consistency with weekly injections is important. If you're gaining weight, speak to your prescriber about dose titration or lifestyle factors.
How long does Mounjaro take to work, and does cost depend on how long I use it?
Most people see appetite reduction within 1–2 weeks at effective doses, with weight loss noticeable after 4–8 weeks. Cost is monthly based on your dose, not on duration — you pay for each month you use it. Private prescriptions are renewed monthly. If you stop Mounjaro, appetite typically returns within 1–2 weeks, which is why consistent access matters.
What's the difference between private cost and NHS access, and how do I know which to choose?
Private costs £129–£320/month but is available immediately with a UK prescriber assessment. NHS is free but has long waiting lists and limited regional availability. If your local NHS can offer Mounjaro quickly, that's ideal. If facing a long wait and you can afford private treatment, many people choose private access for faster results and consistent supply.
Is it cheaper to get Mounjaro on the NHS than privately?
Yes — NHS treatment is free at point of use, but availability is extremely limited. Most NHS areas have waiting lists of 6–18 months for specialist weight management services, and not all areas prescribe Mounjaro yet. If available quickly through your NHS ICB, it's significantly cheaper than private. Check with your GP about local NHS availability before choosing private.
What happens to my weight if I stop using Mounjaro?
Weight typically returns gradually over weeks to months after stopping — appetite suppression wears off within 1–2 weeks. Clinical data shows weight regain of 50% or more is common if lifestyle changes aren't maintained. This is why ongoing access (NHS or private) and concurrent lifestyle change matter for sustainable results. Our progress tracker helps you maintain awareness throughout treatment.
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.