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
Does Mounjaro Always Work in the UK?
Mounjaro isn't a clinically studied weight loss solution—individual results vary significantly. Clinical trials showed that tirzepatide (Mounjaro's active ingredient) helped many people lose weight, but not everyone responds equally. Success depends on your starting weight, lifestyle changes, dose tolerance, and how your body responds. Understanding realistic expectations, costs, and how to access Mounjaro in the UK will help you make an informed decision about whether it's right for you.
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.
How Much Does Mounjaro Cost in the UK?
Private prescription costs for Mounjaro in the UK typically range from £129 to £320 per month, depending on your dose and the provider. Starting doses (2.5 mg and 5 mg KwikPens) are usually cheaper, while higher doses up to the maximum 15 mg cost more. Each KwikPen contains four weekly injections, so one pen lasts approximately one month. Private costs cover the online clinical assessment, prescription, and medication delivery. NHS access is free but limited—Mounjaro is only available through specialist tier 3 or tier 4 weight management services in your local area, and waiting lists can be very long. Regional availability varies significantly across England, Scotland, Wales, and Northern Ireland. Your GP can refer you to NHS specialist services, though many areas have paused or restricted new referrals due to demand.
- Private KwikPen (2.5–5 mg): typically £129–£180/month
- Private KwikPen (7.5–15 mg): typically £200–£320/month
- NHS: free if approved through specialist services
- Additional costs: none if prescribed, though follow-up appointments may apply privately
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.
Mounjaro vs Wegovy Access and What to Expect
Both Mounjaro and Wegovy require a prescription in the UK, but access routes differ. NHS access is free but extremely limited—only available through specialist weight management services with long waiting lists. Private access is faster: you complete an online consultation with a UK-licensed prescriber, answer health questionnaires, and receive a prescription within 24–48 hours if approved. The prescription is dispensed by a GPhC-registered pharmacy and delivered to your home. Private consultations typically cost £20–£50 one-time or per dose cycle. Dose titration takes 16–20 weeks (2.5 mg to 15 mg), so initial costs are lower but increase as you progress to maintenance doses. Use our free GLP-1 weight loss calculator to estimate potential outcomes at different doses, and our BMI calculator to understand your starting point.
- 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 Mounjaro work for everyone?
No. Clinical trials showed that tirzepatide helped most people lose weight, but results vary widely. Some people lose 15–20% of body weight, while others lose less or experience minimal benefit. Success depends on individual factors like metabolism, adherence to diet and exercise changes, dose tolerance, and how your body responds to the medication. Your GP or prescriber can discuss realistic expectations based on your circumstances.
What's the difference between Mounjaro on the NHS and private?
NHS Mounjaro is free but only available through specialist services with often lengthy waiting lists and variable regional availability. Private Mounjaro costs £129–£320/month depending on dose, available quickly via online consultation, and doesn't require NHS referral. Both require prescription and clinical assessment. Private costs include consultation and medication delivery.
How long does it take to see results with Mounjaro?
Most people begin noticing appetite reduction within the first few weeks. Measurable weight loss typically appears after 4–8 weeks of consistent use. Peak effects are usually seen after 16–20 weeks when you reach your target maintenance dose. Results continue improving over time, but individual timelines vary. Lifestyle factors like diet and physical activity significantly influence outcomes.
Can I switch from Wegovy to Mounjaro on the NHS?
Switching between weight loss medications on the NHS is possible but requires discussion with your specialist service. It's not automatic and depends on your individual response, local guidelines, and resource availability. Private providers may offer switching more flexibly. Always consult your prescriber about whether a switch is clinically appropriate for you.
What happens if Mounjaro doesn't work for me?
If you're not responding after 16 weeks at your target dose, your prescriber may explore alternatives like increasing to a higher dose, switching to a different GLP-1 medication, or stopping treatment. Some people respond better to Wegovy or other medications. Your GP or specialist can discuss next steps and ensure you're supported with diet, exercise, and other lifestyle strategies regardless.
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.