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 Can You Lose in a Month on Mounjaro?
Mounjaro (tirzepatide) is a prescription-only GLP-1 and GIP receptor agonist licensed in the UK for weight management. Monthly weight loss varies significantly between individuals and depends on your starting weight, dose, diet, and activity level. Clinical trials showed participants lost an average of 15–21% of their body weight over several months, but results in the first month are typically more modest as your body adjusts to the medication.
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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.
Realistic First Month Weight Loss on Mounjaro
In your first month on Mounjaro, you're likely on a low starting dose of 2.5 mg — a conservative dose designed to allow your body to adapt and minimise side effects. Most users report modest weight loss in weeks 1–4, typically between 1–3 kg, though some experience minimal change as the medication takes time to regulate appetite hormones.
- Week 1–2: Adjustment period; nausea common; appetite may decrease gradually
- Week 3–4: Body adapts; hunger suppression becomes more noticeable; gradual weight loss begins
- Dose escalation matters: Your prescriber will increase your dose every 4 weeks (2.5 mg → 5 mg → 7.5 mg, etc.), and weight loss typically accelerates as you reach higher doses over subsequent months
Remember: weight loss is not assured. Individual results depend on adherence to a reduced-calorie diet, physical activity, metabolism, and genetics. Our GLP-1 weight loss calculator can help you project potential monthly loss at different Mounjaro doses based on clinical trial data.
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.
UK Costs and How to Access Mounjaro
Private prescriptions: In the UK, Mounjaro is available privately through online clinics following a clinical assessment. Monthly costs typically range from £129–£249 per dose depending on which dose you're taking (higher doses cost more). A typical monthly supply covers 4 weekly injections in a KwikPen device.
NHS access: NHS provision is through specialist tier 3 weight management services, usually following GP referral. Availability and waiting times vary significantly by region (ICB). Your GP can advise whether you meet local NHS eligibility criteria, which typically require a BMI of 30+ or 27+ with weight-related health conditions like type 2 diabetes or hypertension. NHS prescription costs are standard item fees (£11.65 or free depending on exemptions).
Use our BMI calculator above to check whether you may meet eligibility thresholds for either route.
Online prescription process: Private providers assess your medical history via online consultation with a UK-licensed prescriber. If approved, a prescription is issued and dispensed by a GPhC-registered pharmacy — no need for GP referral. The consultation typically costs £15–£50 and takes 24–48 hours. You'll receive your first dose within 5–7 working days.
What to expect: Your prescriber will discuss starting at 2.5 mg, how to inject, storage (refrigerate until use, then 30 days at room temperature), and potential side effects. You'll have a follow-up consultation 4 weeks later to review progress and plan your first dose increase. Always inform your prescriber of any other medications, as tirzepatide may affect absorption of oral contraceptives and some diabetes medications.
- 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.
Can I lose 10kg in a month on Mounjaro?
No. Losing 10kg in one month would be unsafe and is not a realistic or recommended target. The NHS advises losing 0.5–1kg per week for sustainable results — approximately 2–4kg per month. Mounjaro supports gradual, steady weight loss through appetite regulation, not rapid loss. Faster loss risks muscle loss and nutritional deficiency.
How does Mounjaro dose titration affect monthly weight loss?
You start at 2.5 mg (low loss, minimal side effects) and increase every 4 weeks. Week 1–4 may see 1–3kg loss; weeks 5–8 on 5mg may see 2–4kg; higher doses (10mg+) often produce 3–5kg per month as your body fully responds. Total loss accelerates over several months, not within a single month.
Is Mounjaro better than Wegovy for monthly weight loss?
Mounjaro is a dual GIP/GLP-1 agonist; Wegovy is GLP-1 only. Clinical trials suggest Mounjaro may produce slightly greater average weight loss (15–21% vs Wegovy's ~15%), but individual variation is huge. Your prescriber will assess which suits you based on medical history, contraindications, and personal factors.
What if I don't lose weight in my first month on Mounjaro?
This is common and not a failure. Many users experience appetite suppression and improved blood sugar control before significant weight loss. Ensure you're in a calorie deficit through diet and activity — Mounjaro supports this but cannot override sustained excessive eating. Discuss with your prescriber if no loss occurs by week 8.
How much does Mounjaro cost per month in the UK?
Private costs range from £129–£249 monthly depending on your dose (5mg, 10mg, 15mg). NHS costs are typically £11.65 per item or free if eligible. Prices vary by provider and region. Compare UK-licensed online providers before committing — costs are transparent upfront.
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.