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 could lose in 3 months depends on your starting point, metabolism, diet, and activity level—there's no one-size-fits-all answer. However, the NHS recommends aiming for a safe, sustainable weight loss of 0.5 to 1 kg (1 to 2 lbs) per week, which means a realistic target over 3 months would be 6 to 12 kg (roughly 13 to 26 lbs). Use our free BMI calculator to find your current healthy weight range for your height, then work backwards to set a realistic 3-month goal aligned with your personal health needs.
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 realistic weight loss timescales
The NHS defines healthy weight loss as 0.5 to 1 kg per week, which translates to approximately 6 to 12 kg over 3 months. This rate is sustainable because it balances fat loss with muscle preservation and is achievable through a combination of dietary changes and increased physical activity. Faster weight loss (more than 1.5 kg per week) is possible but typically requires medical supervision and carries risks including muscle loss, nutrient deficiencies, and metabolic slowdown.
Your actual weight loss will depend on several factors: your starting weight, age, gender, metabolism, calorie deficit, exercise frequency, and sleep quality. Someone with a higher BMI may lose weight faster initially, whilst someone already close to their ideal weight for their height will lose more slowly. Use our BMI calculator to establish your baseline and determine your healthy weight range—this gives you a personalised target rather than a generic number.
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.
Making your 3-month goal realistic and sustainable
Rather than focusing solely on how much weight you could lose, focus on what you can sustain for life. A 3-month goal is most effective when it moves you towards your healthy weight range according to NHS guidelines—not towards an arbitrary number. Break your goal into monthly targets (2 to 4 kg per month is reasonable) and track progress weekly using our free progress tracker, which helps you spot trends rather than daily fluctuations.
Combine dietary changes with physical activity: aim for a 500 kcal daily deficit through diet, then add 150 minutes of moderate activity per week for additional results. If you're significantly overweight or have health conditions, consult your GP before starting, especially if considering prescription weight loss support or very low-calorie approaches.
- 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 safe?
Yes, 12 kg over 3 months (4 kg per month, roughly 1 kg per week) is within NHS safe guidelines. Anything faster than 1 kg per week is typically only advised under medical supervision. Consistency matters more than speed—sustainable weight loss is more likely to stay off long-term than rapid loss.
How do I know my healthy weight target for 3 months?
Calculate your BMI using our free BMI calculator to find your healthy weight range for your height. The NHS healthy range is BMI 18.5 to 24.9. If you're currently overweight, aim to shift your BMI down by 1 to 2 points in 3 months—this is realistic and health-focused rather than appearance-focused.
Does my diet or exercise matter more for weight loss?
Both matter, but weight loss is primarily driven by calorie deficit—roughly 80% diet, 20% exercise. Create a 500 kcal daily deficit through diet changes, then add exercise for cardiovascular health and muscle preservation. This combination is more effective than exercise alone.
Can prescription weight loss injections help me lose more in 3 months?
Prescription weight loss medications like Mounjaro and Wegovy are available on the NHS or privately following clinical assessment. Clinical trials show average weight loss of 15–21% over several months alongside diet and exercise. Eligibility requires a BMI of 30+ or 27+ with health conditions. Always discuss options with your GP.
Should I weigh myself every day to track 3-month progress?
Daily weighing can be discouraging due to water retention and hormonal fluctuations. Weekly weighing on the same day, at the same time, gives a truer picture. Use our free progress tracker to log weekly weights and spot the overall downward trend rather than obsessing over daily changes.
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.