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
Does Mounjaro Boost Metabolism?
Mounjaro (tirzepatide) doesn't directly boost your resting metabolic rate in the traditional sense. Instead, it works by activating GIP and GLP-1 hormone pathways that regulate appetite, reduce food cravings, and help you feel fuller after smaller meals. The weight loss you achieve comes primarily from eating less, not from burning more calories at rest. Understanding how Mounjaro actually works — and how to access it in the UK — can help you decide if it's 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.
How Mounjaro Affects Your Metabolism and Weight Loss
Mounjaro is a dual GIP and GLP-1 receptor agonist, which means it activates two natural hormone pathways involved in appetite regulation and blood sugar control. When you take a once-weekly injection of tirzepatide via KwikPen, these hormones signal to your brain that you're satisfied, which typically leads to reduced food intake — the primary driver of weight loss in clinical trials.
In the SURMOUNT-1 trial, people taking the maximum 15mg dose lost an average of 20.9% of their body weight over 72 weeks, though individual results vary significantly. This weight loss occurred alongside a reduced-calorie diet and increased physical activity. Mounjaro also slows gastric emptying (how quickly food leaves your stomach), though this effect often reduces over time as your body adjusts. Your resting metabolic rate itself doesn't increase — the weight loss comes from consuming fewer calories because you feel fuller and less hungry.
- Activates appetite-suppressing hormones (GIP and GLP-1)
- Reduces food cravings and hunger signals
- Helps portion control and meal satisfaction
- Does not increase calorie-burning at rest
- Works best alongside diet and exercise changes
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 and Access in the UK
In the UK, you can access Mounjaro through two main routes: NHS specialist weight management services or private prescription through an online prescriber. NHS access requires referral to a tier 3 or tier 4 specialist weight management service from your GP, but availability varies dramatically by region and waiting lists can be very long — sometimes 6 months to 2+ years depending on your area.
Private online prescription is faster: a UK-licensed prescriber conducts an online clinical assessment, and if approved, your prescription is dispensed by a GPhC-registered pharmacy. Private costs typically range from £150–£300 per month depending on your dose and the provider. Remember, Mounjaro requires a valid prescription and is not suitable for everyone — pregnancy, certain medical conditions, and medication interactions must be assessed individually by your prescriber.
- 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.
Does Mounjaro speed up my metabolism permanently?
No. Mounjaro works by reducing appetite and food intake, not by increasing your resting metabolic rate. Once you stop taking it, your metabolism returns to baseline. Weight loss happens because you eat less, not because you burn more calories at rest. This is why combining Mounjaro with sustainable diet and exercise changes is important for long-term results.
How much weight can I expect to lose on Mounjaro?
Clinical trials showed an average weight loss of 15–21% of body weight over 72 weeks at higher doses, but individual results vary significantly. Some people lose more, some less. Weight loss depends on your starting weight, adherence to a reduced-calorie diet, physical activity level, and individual metabolism. Your prescriber can give personalised expectations based on your health profile.
Can I get Mounjaro on the NHS in the UK?
Yes, but access is limited. NICE has approved tirzepatide for NHS use within specialist weight management services (tier 3/4). You need a GP referral, and availability varies by region with significant waiting lists in many areas. Private online prescription is often faster but comes at a cost of roughly £150–£300 per month depending on dose.
What's the difference between Mounjaro and Wegovy for weight loss?
Both are prescription-only injections, but Mounjaro is a dual GIP+GLP-1 agonist, while Wegovy (semaglutide) is a GLP-1-only agonist. Clinical trial data suggests Mounjaro may produce slightly greater average weight loss (20.9% vs 14.9%), though results vary. Mounjaro requires dose titration starting at 2.5mg weekly up to 15mg; Wegovy starts at 0.25mg escalating to 2.4mg. Your prescriber will assess which suits you better.
Do I need to diet and exercise while taking Mounjaro?
Yes. Mounjaro is most effective when combined with a reduced-calorie diet and increased physical activity. The medication helps suppress appetite, but it doesn't burn calories for you. NHS guidance and clinical trials show that sustainable weight loss requires both medication and lifestyle change. Using our free GLP-1 weight loss calculator can help you estimate potential results with consistent dietary and exercise efforts alongside treatment.
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.