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
Weight Loss Time Estimator: How Long Until Results?
Wondering how long weight loss takes? The answer depends on your starting point, chosen method, and individual factors. The NHS recommends losing weight at a rate of 0.5 to 1 kg per week for sustainable, healthy results. Using our free BMI calculator and weight loss projection tools, you can estimate realistic timescales based on your personal circumstances. This guide explains how to calculate your own weight loss timeline using evidence-based methods, whether through calorie deficit alone or with the support of prescription weight loss medication. Individual results vary significantly, but understanding the timeline helps you set achievable goals.
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.
Calculating Weight Loss Timeline: The Science
Weight loss speed depends on calorie deficit — the difference between calories consumed and calories burned. The NHS guidance is clear: a deficit of around 500 kcal per day typically results in a loss of approximately 0.5 kg per week. A larger deficit of 1,000 kcal per day may produce roughly 1 kg per week loss, though faster loss increases muscle loss risk and is not sustainable long-term.
To estimate your timeline, calculate your target weight loss and divide by your weekly loss rate. For example, losing 10 kg at 0.5 kg per week would take approximately 20 weeks (5 months). However, this is a general estimate — actual results depend on your age, metabolism, activity level, diet quality, and whether you're using prescription weight management medication.
Our GLP-1 weight loss calculator can help you project potential results if you're considering medication-assisted weight loss in the UK. Use our progress tracker to log your actual results and adjust your goals as needed.
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.
Weight Loss Medication and Timeline: GLP-1 Options
Prescription weight loss medications such as Wegovy (semaglutide) and Mounjaro (tirzepatide) may accelerate weight loss when used alongside a reduced-calorie diet and increased physical activity. Clinical trial data shows that on average, adults using these GLP-1 medications achieved approximately 15–clinically studied weight loss over 68–72 weeks — significantly more than diet alone.
However, these medications require a clinical assessment and prescription from a UK-licensed prescriber. They are not a shortcut but a tool to support behaviour change. Weight loss medication NHS access varies by region, available through specialist tier 3 weight management services with waiting times that can extend months to years in some areas. Private prescribing is also available, but individual results vary considerably. Always discuss realistic timelines with your healthcare provider.
- 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 long does it take to lose 10 kg?
At a safe rate of 0.5 kg per week (NHS recommended), losing 10 kg would take approximately 20 weeks or about 5 months. At 1 kg per week, approximately 10 weeks (2.5 months). However, individual timelines vary based on starting weight, metabolism, activity level, and diet consistency. Faster loss increases muscle loss risk.
Can weight loss injections speed up the timeline?
Clinical trials show that GLP-1 medications like Wegovy may support faster weight loss alongside lifestyle changes. STEP trial data showed average losses of 15% body weight over 68 weeks. However, prescription weight loss medications are not assured, individual results vary significantly, and they require clinical assessment and a valid prescription.
What's the fastest safe way to lose weight?
The NHS recommends losing 0.5 to 1 kg per week as safe and sustainable. Faster loss (over 1.5 kg per week) risks muscle loss, nutritional deficiency, and unsustainable patterns. Very rapid loss should only be attempted under medical supervision, such as through NHS specialist weight management services.
Why does weight loss slow down over time?
As you lose weight, your body requires fewer calories to maintain itself (adaptive thermogenesis). This means the same calorie deficit becomes less effective. You may need to increase physical activity or adjust your diet to continue losing weight at the same rate — a common plateau around 3–6 months.
How can I track my actual weight loss progress?
Use our free progress tracker to log your weight weekly and visualise your trend over time. Our BMI calculator shows how your weight loss affects your BMI category. Tracking helps you spot patterns, adjust goals, and stay motivated. Remember to weigh yourself at the same time of day, as weight naturally fluctuates.
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.