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
How Much Weight Could I Lose In 3 Months?
The amount of weight you can realistically lose in three months depends on your starting weight, metabolism, diet, and activity level. The NHS recommends aiming for a loss of 0.5 to 1 kg (1 to 2 lbs) per week for sustainable, healthy results. This means a realistic target for three months would be 6 to 12 kg (13 to 26 lbs), though individual results vary significantly. Use our free BMI calculator and GLP-1 weight loss calculator to understand your personal starting point and explore potential outcomes based on your circumstances.
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.
Safe Weight Loss Rate And What It Means For 3 Months
The NHS advises that losing 0.5 to 1 kg per week is the safe, sustainable rate for most adults. This pace helps preserve muscle mass, supports long-term habit change, and reduces the risk of nutrient deficiencies or metabolic slowdown.
Over a 12-week period (roughly 3 months), this translates to:
- Conservative pace (0.5 kg/week): approximately 6 kg total loss
- Standard pace (0.75 kg/week): approximately 9 kg total loss
- Brisk pace (1 kg/week): approximately 12 kg total loss
Faster loss is technically possible—particularly in the first 2–3 weeks when water weight contributes significantly—but gradual weight management often leads to muscle loss, fatigue, and difficulty maintaining results. A calorie deficit of roughly 500 kcal per day produces approximately 0.5 kg loss per week. For faster loss, deficits can reach 750–1000 kcal/day, but this should only be done under medical supervision.
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.
Factors That Affect Your Personal Weight Loss In 3 Months
Weight loss isn't one-size-fits-all. Your age, gender, metabolism, starting weight, and exercise routine all influence how much you'll lose. People with higher starting weights often lose more in absolute terms initially. Your healthy weight range depends on your height and ethnicity—use our weight converter and BMI calculator to check what the NHS considers healthy for you. Diet quality, sleep, stress levels, and any underlying health conditions also play a role. Prescription weight loss medications like Mounjaro or Wegovy, used alongside lifestyle changes, may significantly increase results for eligible individuals. Even modest losses of 5% of body weight can improve blood pressure, blood sugar control, and cardiovascular health.
- 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 losing 12 kg in 3 months realistic?
For most people, yes—at the NHS-recommended rate of 1 kg per week. However, this requires consistent effort with diet and exercise. First-week losses are often higher (water weight), then stabilise. Individual variation is significant, so progress tracking with our free progress tracker helps maintain realistic expectations.
What's the fastest safe weight loss in 3 months?
The NHS recommends no more than 1 kg per week, meaning 12 kg maximum over 3 months for most adults. Faster loss risks muscle loss and metabolic disruption. Very rapid loss (>1.5 kg/week) should only occur under medical supervision and is not advisable for most people.
Will I keep weight off after 3 months?
Sustainable weight loss depends on whether the changes become permanent habits. Rapid, restrictive approaches often lead to rebound weight gain. Focus on building lasting dietary and activity patterns rather than extreme short-term losses.
How does prescription weight loss medication affect 3-month results?
Medications like Mounjaro or Wegovy, prescribed following clinical assessment, may increase weight loss when combined with diet and exercise changes. Clinical trials show average losses of 15–21% of body weight over longer periods, though results vary and require prescription.
Should I aim for my ideal weight in 3 months?
Your ideal weight depends on your height, age, and frame size. Use our BMI calculator to find your healthy weight range for your height. Reaching it in 3 months may not be realistic if you have significant weight to lose—a longer timeline supports sustainable change and muscle preservation.
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.