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 Much Weight Loss Per Week on Mounjaro?
Weight loss on Mounjaro varies significantly between individuals, but clinical trials showed an average weight loss of 15–21% of body weight over 72 weeks when used alongside a reduced-calorie diet and increased physical activity. This typically translates to approximately 0.5–1 kg per week during the dose escalation phase, though results vary based on starting weight, dose, and individual response. Understanding realistic expectations, UK pricing, and how to access this prescription medication will help you make an informed decision about whether Mounjaro is right for you.
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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 Weight Loss Expectations & Weekly Progress
Clinical trial data from SURMOUNT-1 provides the most reliable guide to expected weight loss on Mounjaro. At the maximum dose of 15 mg, participants lost an average of 20.9% of their body weight — though individual results ranged from minimal loss to 30% or more. Weekly weight loss is not consistent: the first 4–8 weeks (during dose escalation) typically show faster loss as the body adjusts to the medication, while weeks 9 onwards tend to show a slower, steadier rate.
- Weeks 1–8: Often 0.5–1.5 kg per week (variable, dose-dependent)
- Weeks 9+: Typically 0.3–0.8 kg per week as weight loss stabilises
- Maximum expected loss: 20–21% of starting body weight over 72 weeks
- Critical factor: Mounjaro works best alongside reduced-calorie diet and exercise — medication alone does not clinically studied weight loss
Use our GLP-1 weight loss calculator to estimate your potential weight loss at different Mounjaro doses based on your current weight and height.
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 Cost & Access in the UK
NHS access: NICE has approved tirzepatide (Mounjaro) for use within NHS specialist weight management services, but access is limited. You need a GP referral to a tier 3 or 4 specialist weight management service in your area. Waiting lists can be 6–18 months depending on your region, and some ICBs have restricted access criteria.
Private access: Available through GPhC-registered online prescribers following a clinical assessment. Private costs typically range from £129–£320 per month depending on dose and provider — a 2.5 mg starting dose costs less than the 15 mg maximum dose. You receive a prescription and choose your preferred GPhC-registered pharmacy to dispense it.
What to expect: Both routes require a consultation assessing your BMI, medical history, and weight-related health conditions. NHS access is free once prescribed; private prescribing and dispensing incur fees.
- 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.
How much weight can I lose in the first week on Mounjaro?
First-week weight loss varies widely — some people lose 0.5–1 kg, others lose less. Much of early weight loss is water loss, not fat loss. Consistent weekly loss typically establishes after 4–8 weeks as your body adjusts to the medication. Results depend on your starting weight, diet, and activity level.
Is the weight loss on Mounjaro permanent?
Clinical evidence suggests weight loss is maintained while taking Mounjaro. When people stop the medication, weight tends to return gradually over months. Long-term maintenance requires continuing the medication or maintaining lifestyle changes (diet and exercise) learned during treatment.
What's the difference between Mounjaro and Wegovy for weight loss?
Both are prescription weight loss injections, but Mounjaro is a dual GIP and GLP-1 agonist, whilst Wegovy (semaglutide) is a GLP-1 agonist only. Clinical trials showed Mounjaro achieved slightly higher average weight loss (20.9% vs ~15%), but both are effective. Results vary individually. Both are once-weekly injections requiring a UK prescription.
Can I get Mounjaro on the NHS in the UK?
Yes — NICE approved Mounjaro for NHS specialist weight management services. However, access varies significantly by region (ICB). You need a GP referral to tier 3 specialist services, and many areas have long waiting lists. Private access is faster but involves fees. Ask your GP about local NHS availability.
How long does a Mounjaro KwikPen last?
Each KwikPen contains four weekly doses — so one pen lasts four weeks. Costs vary by dose: a 2.5 mg pen (starting dose) costs less than a 15 mg pen (maximum dose). Private pricing typically ranges £129–£320 per month depending on the dose and provider.
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.