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
What Does Mounjaro Feel Like vs Wegovy?
Mounjaro and Wegovy are both prescription-only weight management injections available in the UK, but they work slightly differently and may feel different during use. While both can help with appetite control and weight loss, your personal experience with Mounjaro depends on the dose, your individual physiology, and how your body responds to tirzepatide (the active ingredient in Mounjaro). This guide compares what you might experience with each medication based on clinical trial data and NHS guidance.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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 and Wegovy Work Differently
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, meaning it activates two natural hormone pathways simultaneously. This dual mechanism may explain why many users report a stronger appetite-suppressing effect compared to GLP-1-only medications. Wegovy (semaglutide) activates only the GLP-1 pathway, which also reduces appetite but through a single mechanism.
In the SURMOUNT clinical trials, Mounjaro users experienced an average weight loss of 15–21% of their body weight over 72 weeks, whilst STEP trial data for Wegovy showed approximately 15% average loss. The difference in mechanism may affect how soon you feel the appetite-reducing effects and how pronounced they are. Some users report feeling fuller faster with Mounjaro, whilst others notice less difference. Both medications slow how quickly food leaves your stomach, which contributes to the feeling of fullness. Your GP or prescriber can discuss which mechanism may suit your individual circumstances better.
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.
What the Experience Is Actually Like
Most Mounjaro users report that appetite changes develop gradually over the first 2–4 weeks as their body adjusts. Initially, many notice reduced interest in food they normally enjoy, smaller portion sizes feeling satisfying, and reduced cravings between meals. Common physical sensations include mild nausea (particularly in the first 1–2 weeks), which typically improves as the body adjusts. Some users experience changes in taste preferences or mild stomach discomfort when eating, especially if they eat too quickly or too much.
Practical tip: Use our free GLP-1 weight loss calculator to estimate potential results at different doses, and our BMI calculator to track baseline measurements. Side effects and sensations vary significantly between individuals—what one person experiences may differ completely from another's experience.
Both Mounjaro and Wegovy require a UK prescription and clinical assessment before starting. Your prescriber will consider your medical history, current medications, and individual health profile. The KwikPen injection itself is small and relatively painless—most users adapt quickly to self-injecting once weekly. Access in the UK is through either NHS specialist weight management services or private online prescribing with a UK-licensed prescriber following clinical assessment. Neither medication is suitable for pregnant women or those planning pregnancy. Starting doses are low (Mounjaro begins at 2.5 mg) and increase gradually every 4 weeks, which allows your body time to adapt and helps minimise side effects.
- 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.
Is Mounjaro or Wegovy better for weight loss?
Clinical trials show similar average weight loss (15–21% for Mounjaro, ~15% for Wegovy), but individual results vary significantly. The "better" option depends on your personal response, medical history, and prescriber recommendation. Your GP can advise which is more suitable following a clinical assessment.
Does Mounjaro nausea go away?
Yes, for most users. Nausea is common in the first 1–2 weeks but typically improves as your body adjusts. Eating smaller, slower meals and staying hydrated can help. If nausea persists beyond 2–4 weeks, contact your prescriber—dose adjustment may help.
How long does it take to feel Mounjaro working?
Most users notice appetite changes within 2–4 weeks of starting. However, some report changes within days, whilst others take longer. Consistent effect builds as you reach maintenance doses (usually by week 8–12). Everyone is different.
Can I switch from Wegovy to Mounjaro?
Switching between medications requires a prescriber's guidance—there is no direct conversion between the two. Your prescriber may recommend stopping one and starting the other at the appropriate starting dose. Never switch without medical supervision.
Is Mounjaro a UK prescription only?
Yes. Mounjaro is a prescription-only medicine in the UK. You cannot buy it without a valid prescription from a UK-licensed prescriber. Access is through NHS specialist services or private online prescribing following clinical assessment.
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.