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
Mounjaro 2.5mg vs 5mg — Weight Loss Dose Comparison
Mounjaro (tirzepatide) is started at 2.5mg and escalated to 5mg after four weeks — but what's the difference between these doses for weight loss? The 2.5mg dose is a starting dose used to allow your body to adjust, while 5mg is the first maintenance dose where most weight loss begins. Both are prescription-only weekly weight loss injections available in the UK through NHS specialist services or private prescribing. Individual results vary significantly, and your prescriber will manage your dose progression based on how well you tolerate the medication and your response to treatment.
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.
Mounjaro Dose Escalation and Expected Weight Loss
Mounjaro uses a dose titration schedule — starting low and gradually increasing to allow your body to adapt and minimise side effects. The 2.5mg dose is taken for weeks 1–4 as your starting dose. After four weeks, if tolerated well, you escalate to the 5mg dose, which is typically continued for weeks 5–8 and often becomes the first maintenance dose where noticeable weight loss occurs.
In clinical trials (SURMOUNT-1), participants on 5mg saw average weight loss of approximately 15% of body weight at 72 weeks, whilst those on 2.5mg saw lower results. However, individual responses vary considerably — some people see significant weight loss at 5mg, whilst others require higher doses (7.5mg, 10mg, 15mg) for optimal results.
- 2.5mg (weeks 1–4): Adjustment phase, minimal weight loss expected, allows tolerance assessment
- 5mg (weeks 5–8+): First maintenance dose, noticeable weight loss typically begins here
- Each dose is administered once weekly as a Mounjaro KwikPen injection
- Minimum 4 weeks on each dose before escalation
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.
NHS Prescribing and UK Dose Access
In the UK, Mounjaro for weight management is prescribed through NHS tier 3 specialist weight management services following NICE guidance. Access is typically via GP referral to your local integrated care board (ICB), though waiting times vary significantly by region — some areas have months-long waiting lists. Private prescribing routes allow faster access through GPhC-registered online pharmacies and licensed prescribers, bypassing the NHS queue.
Your prescriber will assess whether you're eligible (BMI ≥30, or BMI ≥27.5 with weight-related health conditions for certain ethnic backgrounds) and determine your starting dose. Use our free GLP-1 weight loss calculator to estimate potential results at different doses, and our BMI calculator to understand your current weight category and eligibility threshold for UK prescribing.
- 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.
Why does Mounjaro start at 2.5mg and not 5mg?
The 2.5mg starting dose allows your body to adapt gradually and helps identify side effects before escalating. Gastrointestinal side effects (nausea, constipation) are common at higher doses, so starting low reduces severity. After four weeks, if tolerated well, you progress to 5mg — the first maintenance dose where meaningful weight loss typically begins.
Is 5mg the highest dose of Mounjaro in the UK?
No. 5mg is the first maintenance dose, but Mounjaro escalates up to a maximum of 15mg once weekly. Your prescriber may increase you beyond 5mg (to 7.5mg, 10mg, 12.5mg, or 15mg) if 5mg isn't giving sufficient weight loss results, or if you tolerate higher doses well.
How much weight loss can you expect on Mounjaro 5mg?
In clinical trials, average weight loss on 5mg was approximately 15% of body weight at 72 weeks, alongside a reduced-calorie diet and increased physical activity. However, individual results vary widely — some people lose more, some less. Your prescriber will assess your progress at each dose level.
Can I skip 5mg and start at a higher Mounjaro dose?
No. UK prescribing guidelines and manufacturer recommendations require starting at 2.5mg and escalating every four weeks. Skipping doses increases side effects risk and isn't supported by clinical evidence. Your prescriber will follow the established titration schedule.
How do I access Mounjaro 2.5mg and 5mg on the NHS in the UK?
Request a referral to your local NHS tier 3 weight management service from your GP. They'll assess eligibility and prescribe Mounjaro following NICE guidance. Alternatively, private online prescribing offers faster access through a licensed prescriber and GPhC-registered pharmacy, though costs apply.
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.