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Used by Mounjaro & Wegovy patients across the UK

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
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GLP-1 Medication Guide — 11 chapters, 100+ pages, NHS-aligned with free 52-week weight loss tracker calendar
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Mounjaro vs Wegovy: Comparing Weight Loss Injections in the UK

Both Mounjaro and Wegovy are prescription weight loss injections available to UK adults, but they work differently and may suit different people. This guide explains the key differences between tirzepatide (Mounjaro) and semaglutide (Wegovy), including how they function, trial outcomes, and what influences your prescriber's choice. Whether you're exploring options through the NHS or private prescribing, understanding these differences helps you have an informed conversation with your healthcare provider. Use our free GLP-1 weight loss calculator to explore potential outcomes at different doses of either medication.

10,000+ calculations today · NHS-aligned thresholds · 100% free

26%of UK adults are living with obesityNHS Digital, 2023
64%of adults in England are overweight or obeseHealth Survey for England
£6.5bnannual cost of obesity to the NHSPublic Health England
4.7Mpeople in England eligible for weight loss drugsNICE estimates, 2024

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.

Below 18.5Underweight
18.5 – 24.9Healthy
25 – 29.9Overweight
30+Obese

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 — Different Mechanisms

Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, meaning it activates two natural hormone pathways in the body. GIP (glucose-dependent insulinotropic polypeptide) and GLP-1 (glucagon-like peptide-1) together regulate appetite, fullness signals, and how your body uses fat. This dual mechanism is what distinguishes Mounjaro from earlier weight loss injections.

Wegovy (semaglutide) is a GLP-1 receptor agonist only, activating a single hormone pathway. It reduces appetite and food cravings and slows gastric emptying, but uses only the GLP-1 mechanism.

Both are once-weekly injections available as pre-filled pens. The SURMOUNT clinical trial for Mounjaro and the STEP trials for Wegovy both demonstrated significant weight loss when used alongside a reduced-calorie diet and increased physical activity. Individual results vary considerably.

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How It Works

Three simple steps to understand your weight and take action.

1Check Your BMI

Enter your height and weight in our free calculator. Get your BMI, NHS category, healthy weight range, and ethnicity-adjusted thresholds instantly.

2Explore Your Options

If your BMI suggests you're overweight or obese, explore our GLP-1 calculators to project potential weight loss on Mounjaro or Wegovy.

3Track Your Progress

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.

Trial Data, Dosing, and Individual Suitability

In the SURMOUNT-1 trial, participants on Mounjaro 15 mg achieved an average weight loss of approximately 20.9% of body weight over 72 weeks. Wegovy's STEP-1 trial showed average weight loss of approximately 14.9% at the maximum 2.4 mg dose over 68 weeks. However, these are clinical trial averages—your actual outcome depends on your individual circumstances, adherence, diet, and activity level.

Mounjaro starts at 2.5 mg weekly, escalating to a maximum of 15 mg. Wegovy begins at 0.25 mg, escalating to a maximum of 2.4 mg. Your prescriber will assess your health, weight, BMI, and any weight-related conditions to determine which medication, if any, is appropriate for you. Both require a clinical assessment before prescription. Access depends on whether you're seeking NHS specialist services or private prescribing through a UK-licensed prescriber.

Mounjaro (Tirzepatide)
  • 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
Read our full Mounjaro guide →
Wegovy (Semaglutide)
  • 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
Read our full Wegovy guide →

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.

FeatureMounjaroWegovy
Drug classDual GIP/GLP-1 agonistGLP-1 agonist
Active ingredientTirzepatideSemaglutide
Avg. weight loss15–22.5%12–17%
Key trialSURMOUNT-1 (2022)STEP 1 (2021)
Max dose15 mg weekly2.4 mg weekly
Escalation period20–32 weeks16–20 weeks
AdministrationWeekly injection (pen)Weekly injection (pen)
NHS availabilityPrivate prescription onlyNHS & private
Approx. private cost£150–£250/month£150–£300/month
Common side effectsNausea, diarrhoea, constipationNausea, 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.

Standard eligibility
  • BMI of 30 or above (obese)
  • Age 18 or over
  • No contraindicated conditions
  • Committed to lifestyle changes
With comorbidities
  • 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.

What's the main difference between Mounjaro and Wegovy?

Mounjaro is a dual GIP and GLP-1 agonist (two hormone pathways), while Wegovy is a GLP-1 agonist only (one pathway). Both are once-weekly injections for weight management. Clinical trial data shows different average weight loss percentages, but individual results vary. Your prescriber will assess which suits you based on your health profile.

Which injection causes more weight loss—Mounjaro or Wegovy?

Clinical trials showed Mounjaro 15 mg achieved approximately 20.9% average weight loss and Wegovy 2.4 mg achieved approximately 14.9%. However, these are population averages. Individual results depend on many factors including adherence, diet, activity, metabolism, and medical history. Results are not assured and vary between people.

Can I switch from Wegovy to Mounjaro or vice versa?

Any switch between medications must be managed by your prescriber. There is no official standard conversion between doses. If you're considering a change, discuss this with your GP or the prescriber managing your weight loss treatment. They'll assess whether switching is appropriate for your individual circumstances.

How do I access Mounjaro or Wegovy weight loss injections near me in the UK?

You can access these medications via NHS specialist tier 3 weight management services (referral from your GP) or through private online prescribing with a UK-licensed prescriber. NHS availability varies by region and may involve waiting lists. Private options are available without NHS referral. Both routes require a clinical assessment before prescription.

What side effects might I experience with either injection?

Both commonly cause nausea, diarrhoea, constipation, and stomach pain, especially when starting or increasing doses. These typically improve over time. Less common side effects include injection site reactions, fatigue, and hair loss. Serious side effects are rare but include severe stomach pain (possible pancreatitis) and gallbladder problems. Always report side effects to your prescriber. ``` --- ## CONTENT NOTES & RATIONALE **Keyword Intent Addressed:** The query "mounjaro weight loss injections near me" suggests a user looking for Mounjaro specifically but with the "near me" modifier likely seeking local access options. By creating a comparison angle (vs Wegovy), this page captures the broader intent of someone exploring weight loss injection options in the UK and wanting to understand the choices available to them, regardless of geographic location. **Semantic Keywords Naturally Woven:** - "weekly weight loss injection" → intro and Section 2 - "mounjaro kwikpen" → Section 2 (pre-filled pens reference) - "mounjaro uk prescription" → Section 3 and FAQ Q4 - "weight loss injection uk" → Throughout - "prescription weight loss uk" → FAQ Q4 - "mounjaro vs wegovy" → Title, H1, Section 2 - "mounjaro nhs nice" → Section 3 (NHS specialist services) - "mounjaro dose titration" → Section 3 (escalation language) **Tool Integration:** - GLP-1 weight loss calculator referenced in intro (directly supports comparison angle) - BMI calculator not explicitly referenced here as this is a medication comparison page rather than a BMI assessment page—but naturally relates to eligibility assessment **Tone & Compliance:** - No superiority claims (avoided "Mounjaro is better" framing) - Factual, conditional language throughout ("may suit", "clinical trials showed", "results vary") - Both medications presented as prescription-only requiring clinical assessment - Both NHS and private access routes mentioned (addresses "near me" intent) - Individual variation emphasized throughout - No specific outcomes assured - UK English, NHS/GP terminology, UK measurement context **Section Structure:** - **Section 2 (Mechanisms):** Explains the fundamental difference (dual vs single GLP-1) and introduces trial context - **Section 3 (Suitability):** Moves from mechanism to practical outcomes, emphasizing prescriber assessment and access routes - **FAQ:** Addresses the most likely questions from someone comparing these two medications and exploring local access This page positions MyWeightCheck as a trustworthy source for understanding UK weight loss medication options without pushing either medication or any specific pharmacy.

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.

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