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 Do You Know If Mounjaro Is Working?
When you start taking Mounjaro (tirzepatide), understanding the signs that it's working can help you stay motivated and confident in your treatment. Weight loss isn't always linear, and Mounjaro works differently for everyone, but there are clear markers you can track. This guide explains what to expect, how to monitor your progress, and how to access Mounjaro in the UK through both NHS specialist services and private prescription routes.
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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.
Key Signs Mounjaro Is Working
Weight loss is the most obvious sign, but it's not the only one. Most people taking Mounjaro notice reduced appetite and fewer food cravings within the first few weeks—you may find you feel fuller after smaller meals or lose interest in foods you previously craved. Some people also experience improved energy levels, better blood sugar control (if they have prediabetes or type 2 diabetes), and reduced snacking urges.
- Steady weight loss (typically 0.5–1 kg weekly, though this varies)
- Reduced hunger signals and food cravings
- Feeling fuller on smaller portion sizes
- Improved energy and mood
- Better blood sugar readings (if monitored)
- Clothes fitting differently within 4–8 weeks
Weight changes may not be visible immediately—clinical trials showed that average weight loss with Mounjaro ranges from 15–21% of body weight over 72 weeks at maximum dose, but individual results vary significantly. Some people see faster results; others progress more gradually. Track your progress using our free progress tracker to spot trends rather than focusing on week-to-week fluctuations.
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.
Accessing Mounjaro in the UK: Cost and Routes
NHS access is through NICE-approved tier 3 specialist weight management services—your GP can refer you, but waiting times vary widely by region (ICB). Once approved, Mounjaro is typically free on the NHS, though availability remains inconsistent across the country.
Private prescription routes are available through UK-licensed online prescribers following a clinical assessment. Costs range from approximately £129–£320 per month depending on your dose—higher doses cost more because you progress through 2.5 mg, 5 mg, 7.5 mg, 10 mg, 12.5 mg, and finally 15 mg over several weeks. Private access bypasses NHS waiting lists but requires upfront payment. Always check that any provider is registered with the General Pharmaceutical Council (GPhC) and that prescribers are UK-licensed.
- 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 long does it take to notice Mounjaro is working?
Most people notice reduced appetite within 2–4 weeks of starting. Visible weight loss typically becomes measurable after 4–8 weeks, though timings vary. Your dose may be increased every 4 weeks, and stronger effects often follow each escalation. If you've had no appetite changes or weight loss after 8 weeks at 5 mg, discuss this with your prescriber.
What if I'm not losing weight on Mounjaro?
Weight loss depends on dose, adherence, diet, and individual metabolism. Ensure you're following a reduced-calorie diet and increasing physical activity—Mounjaro enhances these efforts but doesn't work without them. Dose increases typically improve results; your prescriber can assess whether dose escalation is appropriate. Some people simply respond differently; discussing this with your healthcare provider is essential.
Is Mounjaro the same as a Mounjaro KwikPen?
Yes—KwikPen is simply the brand name for Mounjaro's pre-filled injection device. Each pen contains 4 weekly doses. Once you've injected all 4 doses, you move to a new pen. The medication inside (tirzepatide) is the same regardless; KwikPen is just the delivery system.
How does Mounjaro compare to Wegovy for weight loss?
Both are once-weekly injections. Mounjaro is a dual GIP and GLP-1 receptor agonist; Wegovy is GLP-1 only. Clinical trials suggest Mounjaro may produce slightly greater average weight loss (15–21% vs 14.9%), but both work well. The best choice depends on your individual response, eligibility, and access. Your prescriber can advise on which suits you better.
Can my GP prescribe Mounjaro, or do I need a specialist?
NHS Mounjaro is typically prescribed through tier 3 specialist weight management services following NICE guidance—your GP refers you but doesn't usually prescribe directly. Private prescribers can issue Mounjaro prescriptions online if you meet eligibility criteria (BMI ≥30, or ≥27 with weight-related health conditions). Check that any private prescriber is UK-licensed and GPhC-registered.
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.