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
Can I Stay On 2.5 Mounjaro For Weight Loss?
The short answer: staying on the 2.5 mg starting dose is unlikely to deliver optimal weight loss results, and NHS and clinical guidance recommend dose titration. The 2.5 mg dose is designed as an adjustment phase to allow your body to adapt — not as a maintenance dose. Most people progress to 5 mg and higher weekly weight loss injection doses over 16–20 weeks to achieve meaningful weight loss. Your prescriber will discuss whether stepping up doses is right for you based on your individual response and tolerance.
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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 Does NHS Guidance Say About Mounjaro Dosing?
NICE and NHS guidance on Mounjaro (tirzepatide) is clear: dose escalation is part of the standard treatment protocol. The 2.5 mg dose is your starting point only — it's an induction phase to help your body tolerate the medication and adjust to GIP and GLP-1 receptor activation. Clinical trial data shows that staying on 2.5 mg delivers minimal weight loss — typically less than 5% of body weight. To achieve the 15–clinically studied weight loss seen in SURMOUNT trials, patients need to progress through the dose range: 2.5 mg (weeks 1–4), then 5 mg (weeks 5–8), continuing upwards every 4 weeks as tolerated, up to the 15 mg maximum dose. NHS specialists will assess your individual tolerance and health factors, but the protocol assumes progression. If you experience significant side effects at 2.5 mg, your doctor may extend the timeline before increasing — but remaining on 2.5 mg long-term is not standard practice and won't deliver substantial 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.
Free Weight Loss Tools & Guides
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
Weight Loss Expectations: 2.5 mg vs Higher Doses
In clinical trials, participants on 2.5 mg Mounjaro averaged only 3–clinically studied weight loss over 72 weeks — significantly lower than those who reached 5 mg (approximately 15% loss) or 15 mg (approximately 21% loss). If you're hoping for meaningful weight loss, staying at the starting dose means missing the therapeutic benefit of the medication. Your GP or NHS weight management specialist can use our free GLP-1 weight loss calculator to project potential results at different doses — this helps visualise why dose progression matters for your goals. Alongside this, our BMI calculator can track where you stand now and where NHS healthy weight targets fall for your height, helping you set realistic milestones as your dose increases.
- 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 is 2.5 mg Mounjaro just a starting dose and not a maintenance dose?
The 2.5 mg dose is an induction phase — it allows your gut to adapt to the medication and minimises side effects like nausea. Clinical data shows it delivers less than clinically studied weight loss. Dose escalation every 4 weeks is the standard NHS protocol to reach therapeutic levels needed for meaningful weight loss.
How much weight can you lose on 2.5 mg Mounjaro alone?
Clinical trials show approximately 3–clinically studied weight loss on 2.5 mg over 72 weeks — much lower than higher doses. Most people need to progress to 5 mg or above to see substantial results aligned with NHS weight management targets.
What happens if I experience side effects on 2.5 mg — can I stay on it longer?
If side effects are severe, your prescriber may extend the induction phase at 2.5 mg before increasing the dose. However, prolonging this phase indefinitely isn't recommended because you won't achieve adequate weight loss. Your NHS specialist will discuss tolerance management and timing.
How quickly should I progress from 2.5 mg to higher Mounjaro doses?
Standard NHS protocol increases the dose every 4 weeks — moving from 2.5 mg to 5 mg, then 7.5 mg, and so on. Each increase is only made if you're tolerating the previous dose well and your weight loss is progressing. Your prescriber sets the exact timeline based on your individual response.
Can I use MyWeightCheck tools to plan my Mounjaro dosing?
Yes — our free GLP-1 weight loss calculator helps you estimate potential weight loss at different doses based on clinical trial data. Our BMI calculator shows your current health weight status and targets. Use these alongside your prescriber's guidance to understand your weight loss journey.
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.