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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How Quickly Does Mounjaro Start Working in the UK?
Mounjaro (tirzepatide) begins working within the first few days, but noticeable weight loss typically takes 4–8 weeks of consistent use. In this guide, we explain the timeline for seeing results, break down UK private prescription costs, and compare NHS vs private access routes. Whether you're considering Mounjaro through an NHS specialist service or exploring private prescription options, understanding the cost, eligibility, and timeline helps you make an informed decision. Use our free GLP-1 weight loss calculator to estimate potential results, and read on for practical information about accessing this medication in the UK.
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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.
Mounjaro Cost and Private Prescription Access in the UK
Mounjaro is available in the UK through two main routes: NHS specialist weight management services and private prescription via online consultations with UK-licensed prescribers. Private prescription costs typically range from £129 to £320 per month, depending on your dose and the provider. A single Mounjaro KwikPen (containing four weekly doses) costs between £130 and £280 privately, making it approximately £32.50 to £70 per weekly injection at maintenance doses.
- 2.5 mg starting dose: lower cost (around £129–£150)
- 5–10 mg maintenance: mid-range cost (around £160–£220)
- 15 mg maximum dose: higher cost (around £280–£320)
These prices vary between providers and may include consultation fees (typically £20–£50). NHS access through tier 3 specialist services is free but often involves waiting lists of several months to over a year depending on your region and local Integrated Care Board (ICB) capacity. NICE (the National Institute for Health and Care Excellence) has approved tirzepatide for NHS use, but regional availability remains inconsistent across England, Scotland, Wales, and Northern Ireland.
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: Timeline and How to Get Mounjaro
NHS route: Referral to tier 3 specialist weight management service from your GP, followed by assessment and prescription if you meet eligibility criteria (BMI ≥30 or BMI 27–29.9 with weight-related health conditions). This route is free but waiting times can be 6–18 months depending on your area.
Private route: Complete an online consultation with a UK-licensed prescriber, usually within 24–48 hours. If approved, your prescription is sent to a GPhC-registered pharmacy and delivered to your home. No NHS referral needed. Most people can start within 1–2 weeks of initial consultation. Once started, you'll progress through dose titration over 16–20 weeks before reaching your maintenance dose, which is when weight loss becomes most noticeable. Track your progress with our free progress tracker once you begin treatment.
- 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 with Mounjaro?
Mounjaro begins reducing appetite within days, but visible weight loss typically appears after 4–8 weeks of consistent use. Most people see noticeable results after 8–12 weeks. In clinical trials (SURMOUNT-1), participants achieved average weight loss of 15–21% of body weight over 72 weeks, though individual results vary significantly. Rate of loss depends on dose, adherence, diet, and activity level.
How much does Mounjaro cost privately in the UK?
Private prescription costs range from £129–£320 per month depending on your dose. A single KwikPen (four weekly doses) typically costs £130–£280. Starting doses (2.5 mg) are cheaper; maximum doses (15 mg) are more expensive. Some providers charge additional consultation fees (£20–£50). Always check the total cost with your chosen provider before committing.
Can I get Mounjaro on the NHS in the UK?
Yes, NICE has approved tirzepatide (Mounjaro) for NHS use through specialist tier 3 weight management services. However, NHS access is not assured everywhere, and waiting lists are often very long (6–18 months or more). You'll need a GP referral and must meet strict eligibility criteria. Check with your local ICB to see if tirzepatide is available in your area.
What's the difference between Mounjaro and Wegovy for cost and access?
Both are once-weekly injections licensed for UK weight management. Mounjaro (tirzepatide) is a dual GIP/GLP-1 agonist; Wegovy (semaglutide) is a GLP-1 agonist only. Private costs are similar (£129–£320/month). Both require prescription and clinical assessment. Mounjaro may show weight loss results slightly faster for some people, but individual response varies. Your prescriber will advise which is suitable for you.
How quickly can I start Mounjaro through private prescription?
Private access is typically faster than NHS. Complete your online consultation (usually 24–48 hours), receive your prescription, and have Mounjaro delivered to your home within 1–2 weeks in most cases. You'll then start on a 2.5 mg dose and increase gradually over 16–20 weeks. Use our BMI calculator and GLP-1 weight loss calculator to understand your baseline and estimate potential results before starting.
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.