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 Timeline Calculator — What to Expect in the UK
Understanding your weight loss timeline helps set realistic expectations for your health journey. Whether you're managing weight through lifestyle changes alone or considering prescription weight management options in the UK, knowing realistic timescales can keep you motivated. Our weight loss calculator and BMI tools can help you track your personal progress and understand what a healthy timeline looks like based on your starting point and chosen approach.
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.
UK-Licensed Weight Loss Medication Options and Timescales
Prescription weight management is available in the UK for eligible adults through both NHS and private routes. The three main licensed options are Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide).
Clinical timescales: In trials, most people see initial weight loss within 2–4 weeks, with more significant results by 12–16 weeks. Average weight loss with GLP-1 medications ranges from 15–21% of body weight over 68–72 weeks alongside reduced-calorie diet and increased physical activity.
Eligibility: You may be eligible if you have a BMI of 30 or above, or BMI of 27–29.9 with weight-related health conditions (type 2 diabetes, high blood pressure, sleep apnoea). Eligibility can be assessed through your GP or a licensed prescriber, and timescales for NHS access vary significantly by region.
- Mounjaro: Requires 4–5 months of dose escalation to reach maximum effect
- Wegovy: Similar escalation timeline, maximum 2.4 mg once weekly
- Saxenda: Daily injection with longer escalation period (8–12 weeks)
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.
Realistic Timeline Without Medication — And Finding the Right Approach for You
Lifestyle-only weight loss typically follows the NHS recommendation of 0.5–1 kg per week through a calorie deficit of around 500 kcal daily. At this rate, you would expect to lose approximately 2–4 kg monthly, reaching significant results (5–clinically studied weight loss, which brings real health benefits) within 2–3 months.
The best approach for nhs weight loss in the UK depends on your personal circumstances. Some people achieve sustainable results through diet and exercise alone; others benefit from prescription medication to support their efforts. Your GP can discuss which option suits your health profile. Try our free GLP-1 weight loss calculator above to estimate potential timescales if you're considering prescription weight management, and use our BMI calculator to understand your current health context.
- 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 quickly can I expect to lose weight with prescription medication in the UK?
With GLP-1 medications like Mounjaro or Wegovy, most people see initial changes within 2–4 weeks, with more noticeable weight loss by 8–12 weeks. Clinical trials show average weight loss of 15–21% over 68–72 weeks when combined with dietary changes and exercise. Individual timescales vary significantly.
What's a realistic weight loss timeline without medication?
The NHS recommends losing 0.5–1 kg per week through calorie deficit, which means approximately 2–4 kg monthly. To achieve meaningful health benefits (5–clinically studied weight loss), you'd typically expect 2–3 months of consistent effort with diet and increased physical activity.
How do I know if prescription weight loss medication is right for me?
Eligibility in the UK includes BMI of 30 or above, or BMI 27–29.9 with weight-related conditions like type 2 diabetes or high blood pressure. Speak to your GP about your individual circumstances, or consult with a licensed prescriber through private services for a clinical assessment.
What's the difference between NHS and private weight loss medication access in the UK?
NHS access is through specialist tier 3 services (referral from your GP) and varies by region with potential waiting lists. Private access is through GPhC-registered online prescribers following clinical assessment, available without NHS referral but at personal cost.
Can I use a weight loss calculator to estimate my personal timeline?
Yes — our free GLP-1 weight loss calculator can help estimate potential weight loss at different medication doses. For lifestyle-only approaches, the BMI calculator and progress tracker help you set realistic targets and monitor your actual progress over time. ```
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.