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
Why Aren't You Losing Weight on Mounjaro?
Not seeing weight loss results on Mounjaro? You're not alone — whilst clinical trials showed strong average outcomes, individual responses vary significantly. Some people lose weight steadily, others plateau, and a small percentage see minimal change. Understanding why this happens, exploring your options with your prescriber, and knowing both NHS and private access routes can help you decide next steps. Use our free BMI calculator to track where you stand, and our GLP-1 weight loss calculator to see projected outcomes at different doses.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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.
Why Weight Loss May Plateau or Slow on Mounjaro
Several factors explain why weight loss on Mounjaro may not match clinical trial averages. Dose adequacy is common — you may not yet be on your optimal dose. Mounjaro requires dose titration over 20+ weeks, starting at 2.5 mg and escalating by 2.5 mg every 4 weeks up to 15 mg. Some people need the maximum dose to see meaningful results. Lifestyle factors matter significantly: a weekly weight loss injection works alongside reduced-calorie diet and increased physical activity, not instead of them. Metabolism and genetics play a role — weight loss response varies between individuals due to baseline metabolic rate, hormonal factors, and genetic predisposition. Adaptation can occur — the body may adjust to medication effects over time. Medical conditions like thyroid dysfunction, PCOS, or diabetes complications can reduce weight loss. Finally, expectations may need adjusting — average weight loss across clinical trials was approximately 15–21% body weight, but individual outcomes range from minimal to substantial.
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.
Cost & Access: NHS vs Private Routes in the UK
NHS route: Mounjaro is approved by NICE for NHS specialist weight management services. However, access is limited to tier 3/4 specialist services (not standard GP prescription), requires referral, and availability varies dramatically by region and ICB funding. Many areas have significant waiting lists — sometimes 6–12 months or longer. You pay nothing once prescribed through NHS, but access itself can be the barrier.
Private route: Available through UK-licensed prescribers via online consultation. Typical private costs range from £129–£320 per month depending on your dose — higher doses cost more. You pay for consultation (~£50–£90) plus medication cost. Private access is faster (days to weeks) but requires out-of-pocket expense. Use our GLP-1 weight loss calculator to project outcomes and help justify the investment.
- 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.
What's the typical cost of Mounjaro privately in the UK?
Private Mounjaro costs vary by dose and provider. Starting doses (2.5–5 mg) typically cost £129–£180/month. Mid-range doses (7.5–10 mg) cost £180–£250/month. Maximum dose (15 mg) costs £250–£320/month. Add approximately £50–£90 for online consultation. Costs may differ by provider — always compare before committing.
How long does it take to see weight loss on Mounjaro?
Clinical trials showed weight loss beginning within the first few weeks, with more significant results after 8–12 weeks on adequate doses. However, individual timelines vary. Some see results at 5 mg, others need 10 mg or 15 mg. If you're not seeing change after 12 weeks on your current dose, discuss escalation with your prescriber.
Can I switch from Mounjaro to Wegovy if I'm not losing weight?
Potentially, yes — but only with your prescriber's guidance. Mounjaro is a dual GIP+GLP-1 agonist whilst Wegovy is GLP-1 only. Some people respond better to one mechanism than the other. However, switching requires a new prescription and clinical assessment. Discuss with your prescriber before making changes.
Will increasing my Mounjaro dose help if I'm not losing weight?
Possibly — dose titration is designed to find your optimal response level. If you're on 5 mg or below, escalating to 10 mg or 15 mg may improve results. However, ensure you're also maintaining a calorie deficit and increasing physical activity. Your prescriber should assess whether dose increase is appropriate based on side effects and clinical context.
Is there NHS access to Mounjaro if I'm struggling with costs?
Yes — if you're eligible, NHS specialist weight management services can prescribe Mounjaro free of charge. However, access requires GP referral to tier 3/4 services and varies significantly by region. Ask your GP about local weight management services and referral pathways. Some areas have shorter waiting lists than others, and ICB eligibility criteria differ.
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.