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
Should You Stay On 2.5mg Mounjaro?
Many people wonder whether to remain on the 2.5mg starting dose of Mounjaro or increase to a higher dose. The 2.5mg injection is the initial starting dose of tirzepatide, typically used for the first 4 weeks to allow your body to adjust. Whether you should stay on this dose or progress depends on how you're tolerating it, your weight loss progress, and guidance from your prescriber. This guide explains the dosing approach, what the evidence shows, and when escalation might be considered.
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.
Understanding The 2.5mg Starting Dose
Mounjaro's 2.5mg dose is the starting or "titration" dose — designed to help your body adapt to tirzepatide while minimising side effects like nausea and digestive changes. The standard Mounjaro dosing schedule involves stepping up every 4 weeks: 2.5mg weeks 1–4, then 5mg weeks 5–8, and potentially higher doses in subsequent weeks up to a maximum of 15mg.
However, staying on 2.5mg for longer is sometimes appropriate if you:
- Are experiencing significant side effects that improve when remaining at this dose
- Are achieving meaningful weight loss at 2.5mg
- Have other health conditions that suggest a more cautious approach
- Prefer to monitor progress before escalating
Clinical trial data from the SURMOUNT-1 tirzepatide study showed weight loss occurs at all doses, though higher doses (10–15mg) produced greater average losses. The 5mg dose showed approximately clinically studied weight loss on average.
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.
When To Escalate And When To Stay
Your prescriber will typically recommend dose escalation after 4 weeks if you're tolerating Mounjaro well and want to optimise weight loss potential. If you're experiencing severe nausea, vomiting, or other persistent side effects at 2.5mg, staying on this dose longer — or even pausing escalation — allows time for your body to adapt.
Some people remain on 2.5mg or 5mg long-term because their weight loss goal is being met and side effects remain manageable. There's no requirement to reach the maximum 15mg dose. Using the MyWeightCheck GLP-1 weight loss calculator can help you estimate projected outcomes at different doses, though individual results vary significantly. Always discuss dose progression with your prescriber — they'll assess your tolerance, health profile, and goals before recommending changes.
- 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.
Can I stay on 2.5mg Mounjaro indefinitely?
Yes, if your prescriber agrees and you're achieving your health goals with acceptable side effects. There's no requirement to escalate to higher doses. Dose decisions are individualised based on your tolerance, weight loss progress, and overall health. Always discuss long-term dosing with your prescriber.
How much weight will I lose on 2.5mg Mounjaro?
Weight loss varies significantly between individuals. Clinical trials show 2.5mg is the starting dose; higher doses produce greater average weight losses (5mg ~15%, 10–15mg ~19–21%). Use our GLP-1 weight loss calculator to estimate potential outcomes, but results depend on diet, activity, and individual factors.
What if I experience side effects at 2.5mg?
Common initial side effects (nausea, constipation) often improve within days to weeks. Staying on 2.5mg longer allows your body to adapt. If side effects persist or worsen, inform your prescriber — they may adjust your dose, timing, or recommend dietary changes. Never stop abruptly without medical guidance.
How does Mounjaro 2.5mg compare to Wegovy?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, whereas Wegovy (semaglutide) is a GLP-1 agonist only. Mounjaro's dual mechanism may support different weight loss patterns. Both require prescription and clinical assessment. Comparisons should be discussed with your prescriber.
When should my dose increase from 2.5mg?
Standard practice is to increase after 4 weeks if tolerating well. However, if you're achieving meaningful weight loss and side effects are mild, some prescribers recommend staying longer. Your prescriber will assess your individual response, health goals, and comfort level before recommending escalation.
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.