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 Long Until Mounjaro Starts Working in the UK?
Most people begin noticing the effects of Mounjaro within the first 2–4 weeks, though significant weight loss typically takes 8–12 weeks of consistent use. The timeline depends on your starting dose, individual metabolism, and whether you're following a reduced-calorie diet alongside the injection. In the UK, you can access Mounjaro through NHS specialist services or private prescription following a clinical assessment. Understanding the cost and access routes will help you decide which option suits your situation.
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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 you use. A standard Mounjaro KwikPen contains 4 weeks of injections (4 doses), so monthly costs represent the standard supply. Prices vary because different GPhC-registered online pharmacies set their own costs, and pricing can differ between the starting dose (2.5 mg) and maintenance doses (5 mg to 15 mg). NHS access is free at the point of care for those eligible, but availability is limited and varies significantly by region. Most NHS access is through tier 3 specialist weight management services, requiring a GP referral and often involving substantial waiting lists. The combination of tirzepatide's dual GIP and GLP-1 mechanism means results can be compelling, but you need accurate information about both cost and timeline before starting.
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: How to Access Mounjaro in the UK
NHS route: Request a referral from your GP to your local tier 3 weight management service. Eligibility requires a BMI of 30+ (or 27+ with weight-related health conditions). NHS treatment is free but waiting times can be 6–18 months in many areas depending on your ICB.
Private route: Book an online consultation with a UK-licensed prescriber through a GPhC-registered pharmacy. The consultation typically costs £20–£50. A prescriber will assess your medical history and eligibility (same BMI thresholds apply). If approved, they'll issue a prescription dispensed by the pharmacy. No waiting lists, but you pay the full cost. First supply usually arrives within 2–5 working days.
- 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.
When will I see weight loss results from Mounjaro?
Initial appetite reduction often occurs within 2–4 weeks at the starting dose (2.5 mg). Noticeable weight loss typically begins by weeks 6–8. Most significant results appear after 12–16 weeks as your dose increases through the titration schedule. Individual results vary — some people see faster results, others more gradual. Using our free GLP-1 weight loss calculator can help you estimate potential outcomes based on your dose and lifestyle changes.
Why is Mounjaro more expensive than Wegovy in private prescribing?
Mounjaro and Wegovy often cost similarly in private UK pharmacies. Pricing depends on the individual pharmacy, your dose, and any promotional offers. Compare costs across different GPhC-registered providers before starting — prices can vary by £50–£100 per month. Both are prescription-only and require clinical assessment.
Can I get Mounjaro free on the NHS?
Yes, if you meet eligibility criteria and are referred to an NHS tier 3 specialist weight management service. However, NHS access is limited and regional availability varies significantly. Some ICBs (integrated care boards) have waiting lists of 12–18 months. Your GP can advise on local NHS options in your area.
Do I need a GP appointment before getting Mounjaro privately?
You do not need a GP referral for private Mounjaro. You can book an online consultation directly with a UK-licensed prescriber through a private pharmacy. However, the prescriber will ask for your medical history, so having recent GP records (blood pressure, cholesterol, glucose levels) available is helpful.
How often do I need to take Mounjaro?
Mounjaro is a once-weekly injection. You inject the same day each week using a KwikPen device into your stomach, thigh, or upper arm. Each pen contains 4 weeks of doses. After 4 weeks on each dose during the titration phase, your dose increases (if continuing). Your prescriber will advise your specific schedule.
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.