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
What Results Can You Expect From Mounjaro in 3 Months?
Many people considering Mounjaro want to know what realistic results look like after the first three months of treatment. While individual outcomes vary significantly, understanding the typical timeline—including how the tirzepatide dose titration works in the UK—can help you set reasonable expectations. This guide covers what the clinical evidence shows and how NHS eligibility and private prescribing in the UK affect your treatment pathway.
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.
Realistic Weight Loss in the First 3 Months
Clinical trial data from the SURMOUNT-1 study shows that weight loss occurs gradually over time, with most noticeable changes appearing after 8–12 weeks. In the first three months, participants typically lose between 2–5% of their body weight on average, depending on their starting dose and adherence to a reduced-calorie diet and increased physical activity.
During the initial phase, you'll progress through dose escalation: starting at 2.5 mg, then moving to 5 mg after four weeks. By 12 weeks, many patients are on the 7.5 mg dose. This gradual titration allows your body to adjust and helps minimise gastrointestinal side effects. Weight loss at each dose increase is typically modest at first, with more significant results becoming apparent after 16–20 weeks when you reach a higher maintenance dose.
- Week 1–4 (2.5 mg): minimal weight loss, mainly adjustment period
- Week 5–8 (5 mg): gradual weight loss begins, approximately 1–2 kg average
- Week 9–12 (7.5 mg): continued loss, typically 2–5 kg cumulative
Important: Results vary widely. Some people see faster changes; others progress more slowly. Consistency with diet and exercise significantly affects outcomes.
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 vs Private Access and Realistic Timelines
In the UK, accessing Mounjaro through the NHS involves referral to a tier 3 specialist weight management service—a process that can take several months in many regions. Once treatment starts via the NHS, the same dose titration schedule applies. Private access through a UK-licensed prescriber may be faster, and you can often start within 1–2 weeks of clinical assessment.
Regardless of route, the first three months should be viewed as an adjustment and initiation phase rather than expecting maximum results. Your prescriber will monitor your progress and adjust your dose based on tolerability and weight loss response. Use our free GLP-1 weight loss calculator to estimate potential outcomes at different doses and timeframes, and track your actual progress with our progress tracker.
- 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.
How much weight do most people lose on Mounjaro in 3 months?
On average, 2–5% of body weight in the first three months, based on SURMOUNT trial data. This typically equates to 2–7 kg for most adults, though individual results vary. Much depends on dose, diet, exercise, and individual response. Your GP or prescriber can advise what's realistic for you.
Does weight loss happen quickly or gradually on Mounjaro?
Weight loss is gradual. The first 4–8 weeks may show minimal change as your body adjusts and you're on a lower starting dose (2.5–5 mg). Noticeable weight loss typically becomes apparent from week 8 onwards, with more significant results from week 12 as you reach higher maintenance doses.
What if I don't see results after 3 months on Mounjaro?
If you're not seeing weight loss after 12 weeks, discuss this with your prescriber. It may indicate the need for a dose increase, review of diet and physical activity, or consideration of whether Mounjaro is the right fit. Some people respond more slowly; others may need a different approach.
Is 3 months enough time to decide if Mounjaro is working?
Three months is a reasonable checkpoint but not the final verdict. The SURMOUNT trials ran for 72 weeks; most meaningful results appear after 16–24 weeks. Most prescribers suggest giving treatment at least 4–6 months before making a decision, assuming you're at a therapeutic dose by then.
Can I use MyWeightCheck tools to track my Mounjaro progress?
Yes. Use our BMI calculator monthly to track changes in your BMI, our weight converter to switch between kg and stone easily, and our progress tracker to log weekly weight and measurements—all free and on this site.
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.