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 2.5mg Mounjaro Work — What You Need to Know
The 2.5mg dose is Mounjaro's starting dose, not a maintenance treatment. Clinical evidence shows it's designed to help your body adjust to tirzepatide before moving to higher doses where weight loss effects are more pronounced. Whether 2.5mg "works" depends on what you expect—as a stepping stone in dose titration, it serves an important purpose, but most significant weight loss happens at 5mg and above. Understanding the cost and access routes in the UK will help you decide if Mounjaro is 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.
What the Evidence Shows About 2.5mg Mounjaro
The 2.5mg dose is the mandatory starting point for Mounjaro treatment. In clinical trials, participants remained on 2.5mg for four weeks before escalating to 5mg. At this dose level, weight loss is modest—most participants experienced minimal change in the first month. The real weight loss effects appear when doses reach 5mg, 10mg, and 15mg, where the dual GIP and GLP-1 mechanism becomes more potent.
Research from SURMOUNT trials showed:
- 5mg dose: approximately 15% average body weight loss
- 10mg dose: approximately 19.5% average body weight loss
- 15mg dose: approximately 20.9% average body weight loss
2.5mg serves as dose titration—your body acclimates to the medication while minimising side effects. Nausea and gastrointestinal symptoms are common at higher doses, so starting low allows tolerance to build. Think of 2.5mg as the foundation, not the destination. Most people need to reach at least 5mg to see meaningful weight loss results.
Clinically BackedWeight Loss
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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.
Free Weight Loss Tools & Guides
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
Mounjaro Cost & Access in the UK — NHS vs Private
NHS access: Mounjaro is available through NHS tier 3 specialist weight management services. Eligibility requires referral from your GP, assessment against NICE criteria (BMI 30+, or 27+ with weight-related health conditions), and joining a waiting list—which can be several months to over a year depending on your region. NHS prescribing is free once approved, but availability varies significantly across ICBs.
Private access: Online prescription services can arrange Mounjaro following a clinical consultation with a UK-licensed prescriber. Cost varies by dose: 2.5mg starter packs typically cost £129–£160 per month, whilst maintenance doses (5mg–15mg) range from £160–£320 monthly. You'll need a prescription, which is dispensed by a GPhC-registered pharmacy. Private options avoid NHS waiting lists but involve ongoing costs. Always verify that any service is registered with the MHRA and employs UK-licensed prescribers.
- 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?
The 2.5mg starting dose is usually too low for significant weight loss on its own. It's designed to help your body tolerate the medication. Most weight loss occurs at 5mg and above. You'd typically stay on 2.5mg for just four weeks before escalating to the next dose.
How much does a month of Mounjaro cost in the UK?
Private costs vary between £129–£320 per month depending on dose. The starter 2.5mg dose costs around £129–£160 monthly. Higher doses (10mg–15mg) cost £250–£320. Each KwikPen contains four weekly injections. NHS access is free but requires specialist referral and can involve long waiting lists.
Can I get Mounjaro on the NHS in the UK?
Yes, Mounjaro is available through NHS tier 3 specialist weight management services. You'll need a GP referral, assessment against NICE criteria (BMI 30+, or 27+ with comorbidities), and availability depends on your local ICB. Many areas have significant waiting lists. Private prescribing offers faster access without NHS referral.
What's the difference between Mounjaro and Wegovy?
Mounjaro (tirzepatide) is a dual GIP + GLP-1 agonist, whilst Wegovy (semaglutide) activates GLP-1 only. SURMOUNT trials showed Mounjaro achieved slightly higher average weight loss (20.9% at 15mg vs 14.9% for Wegovy at 2.4mg), though individual results vary. Both are once-weekly injections requiring prescription and clinical assessment.
What happens if 2.5mg Mounjaro doesn't work?
If you tolerate 2.5mg well with minimal side effects, your prescriber will increase your dose to 5mg after four weeks. Each dose escalates every four weeks. If you experience significant side effects on 2.5mg, your prescriber may adjust the timeline or explore alternative treatments. Use our GLP-1 weight loss calculator to estimate potential results at different doses.
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.