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
How Quickly Will Mounjaro Work in the UK?
Mounjaro typically begins supporting weight loss within the first 2โ4 weeks, though individual results vary significantly. Most people notice the strongest effects after 8โ12 weeks of consistent use at therapeutic doses. Weight loss happens gradually alongside a reduced-calorie diet and increased physical activity โ it's not an instant solution. The timeline and cost of accessing Mounjaro in the UK depends on whether you pursue NHS or private prescription routes, each with different waiting times and expenses.
10,000+ calculations today ยท NHS-aligned thresholds ยท 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/mยฒ).
While BMI isn't a perfect measure โ it doesn't account for muscle mass, bone density, or fat distribution โ 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 โ 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 ยฃ149 to ยฃ320 per month, depending on your dose and the provider. The 2.5 mg starting dose is usually at the lower end of this range, whilst higher doses (10 mg to 15 mg) cost more. Each KwikPen contains four weekly doses, so one pen lasts approximately one month. If you're prescribed multiple pens at once, some providers offer modest discounts. NHS access is theoretically free at point of use, but availability is severely limited. Most NHS areas have waiting lists of 6โ18 months for specialist weight management services, and not all regions fund Mounjaro even when referred. Private prescription via a UK-licensed online prescriber is significantly faster โ typically assessments are completed within 24โ48 hours if you meet eligibility criteria.
Clinically BackedWeight Loss
No appointments. No waiting rooms. Just care โ 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 โ 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 โ completely free.
NHS vs. Private Access: Timeline and Process
NHS route: Your GP refers you to a tier 3 specialist weight management service. You'll be assessed for suitability, placed on a waiting list, and prescribed if eligible. This process can take 6 months to 2+ years depending on your region and local ICB funding decisions. Private route: You complete an online consultation with a UK-licensed prescriber (takes 15โ30 minutes). If approved, your prescription is sent to a GPhC-registered pharmacy and dispatched within 24โ48 hours. You'll need to repeat consultations every 3 months to renew prescriptions. Try our GLP-1 weight loss calculator to explore potential outcomes and our BMI calculator to check your eligibility baseline before pursuing either route.
- 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 โ 5mg โ 7.5mg โ 10mg โ 12.5mg โ 15mg
- GLP-1 receptor agonist
- Up to 15โ17% body weight loss (STEP trials)
- Weekly injection, 5-step dose escalation
- NHS & private prescription available
- Doses: 0.25mg โ 0.5mg โ 1mg โ 1.7mg โ 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 | 15โ22.5% | 12โ17% |
| Key trial | SURMOUNT-1 (2022) | STEP 1 (2021) |
| Max dose | 15 mg weekly | 2.4 mg weekly |
| Escalation period | 20โ32 weeks | 16โ20 weeks |
| Administration | Weekly injection (pen) | Weekly injection (pen) |
| NHS availability | Private prescription only | NHS & private |
| Approx. private cost | ยฃ150โยฃ250/month | ยฃ150โยฃ300/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 โ 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 quickly does Mounjaro show weight loss results?
Most people see noticeable weight loss within 8โ12 weeks at therapeutic doses (10 mg or higher). Early weeks (2โ4) may show modest loss or appetite suppression first. Weight loss accelerates as you reach maintenance doses. Results depend on diet adherence, physical activity, starting weight, and individual metabolism โ clinical trials show average weight loss of 15โ21% over 72 weeks.
Is Mounjaro faster than Wegovy for weight loss?
Clinical trials suggest Mounjaro may produce slightly greater average weight loss (tirzepatide's dual GIP/GLP-1 mechanism) compared to Wegovy's single GLP-1 action. However, individual responses vary significantly. Your prescriber will assess which medication suits you based on your health profile and medical history.
Can I get Mounjaro on the NHS in the UK?
Yes, but access is extremely limited. NICE has approved tirzepatide for specialist NHS weight management services, but most regions have long waiting lists (6โ24 months) and restricted funding. Private prescription is available immediately through online consultations with UK-licensed prescribers, though you'll pay monthly costs.
What's the private prescription process for Mounjaro?
Book an online consultation with a GPhC-registered provider. Complete a medical questionnaire and brief video or phone assessment. If approved, your prescription goes to a pharmacy and is dispatched within 24โ48 hours. You repeat this process every 3 months to renew. No GP referral needed.
Do I need to try diet and exercise first before Mounjaro?
NHS and private prescribers will assess your previous weight loss attempts. Mounjaro is prescribed alongside lifestyle changes, not instead of them. You're expected to maintain a reduced-calorie diet and increase physical activity for best results โ the medication supports these efforts rather than replacing them.
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.