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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Does 2.5mg Mounjaro Work — How It Compares to Wegovy
The 2.5mg dose is Mounjaro's starting dose, not typically its therapeutic dose. Clinical trials used higher doses to measure effectiveness. To understand whether 2.5mg Mounjaro works for you, it's important to understand how it compares to Wegovy, what the evidence shows, and how dose escalation works. Both are prescription-only GLP-1 or dual-action weight loss medications available in the UK. Your suitability depends on your individual health profile, not just the medication name. This guide explains the comparison factually so you can discuss options with your GP or prescriber.
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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.
Mounjaro 2.5mg vs Wegovy — Trial Data and Mechanism
The 2.5mg Mounjaro dose is an adjustment phase only—not a maintenance dose. Clinical trials (SURMOUNT-1) measured weight loss at higher doses: 10mg and 15mg achieved approximately 19.5% and clinically studied weight loss respectively. Wegovy (semaglutide), by contrast, uses a single GLP-1 mechanism, whereas Mounjaro is a dual GIP and GLP-1 receptor agonist. This dual action may theoretically offer greater appetite suppression, though individual responses vary significantly.
In the SURMOUNT trials, Mounjaro participants stayed on each dose for a minimum of 4 weeks before escalating. At 2.5mg, most users experience nausea and adjustments in appetite—but meaningful weight loss typically occurs at 5mg and above. Wegovy's clinical trials (STEP-1) showed approximately 14.9% average weight loss at the maximum 2.4mg dose. Both require a reduced-calorie diet and physical activity to achieve results.
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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.
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Which Is Right for You — Prescriber Assessment
Whether 2.5mg Mounjaro "works" depends on your definition and your individual circumstances. At the starting dose, effectiveness is primarily about tolerability—allowing your body to adjust before escalation. Neither Mounjaro nor Wegovy work in isolation; both are prescribed as part of a comprehensive approach including dietary changes and increased physical activity.
Your GP or prescriber will assess your eligibility, medical history, and current medications to decide which medication suits you. Access in the UK comes through NHS specialist services (variable by region and waiting lists) or private prescription following an online clinical assessment. Use our free GLP-1 weight loss calculator to explore potential outcomes at different doses, and our BMI calculator to understand your current health category. Individual results vary—what works well at 2.5mg for one person may require escalation for another.
- 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 2.5mg Mounjaro enough to lose weight?
2.5mg is a starting dose designed for adjustment, not weight loss. Most weight loss occurs at 5mg and above. Nausea at 2.5mg is common and typically reduces as your body adjusts. Your prescriber will increase your dose every 4 weeks until you reach an effective maintenance dose. Weight loss at 2.5mg alone, without dose escalation, is usually minimal.
How does Mounjaro's mechanism differ from Wegovy?
Mounjaro is a dual GIP and GLP-1 receptor agonist—it activates two hormone pathways. Wegovy is a GLP-1 agonist only (single pathway). The dual mechanism may offer greater appetite suppression, but both medications show similar average weight loss percentages in clinical trials when used at their effective doses.
What does the SURMOUNT trial show about Mounjaro effectiveness?
SURMOUNT-1 tested Mounjaro at 5mg, 10mg, and 15mg doses. At 10mg, participants lost approximately 19.5% of body weight; at 15mg, approximately 20.9%—both after 72 weeks alongside diet and exercise. The 2.5mg dose was not evaluated for weight loss; it's purely a titration step.
Can I stay on 2.5mg Mounjaro long-term?
No. 2.5mg is a temporary adjustment dose. Your prescriber will increase it every 4 weeks until you reach an effective maintenance dose (usually 5mg–15mg for Mounjaro). Staying at 2.5mg would not provide meaningful weight loss for most people.
How do I access Mounjaro or Wegovy in the UK?
Both require a prescription from a UK-licensed prescriber following a clinical assessment. NHS access is through tier 3 specialist weight management services (referral from your GP; availability and waiting lists vary by region). Private access is through registered online clinics and pharmacies. Eligibility typically requires BMI ≥30, or BMI 27–29.9 with weight-related health conditions.
Ready to take control of your weight loss journey?
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