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 Loss Per Week With Orlistat?
Orlistat is a prescription weight loss medication available on the NHS, but realistic expectations matter. Most people lose 2–3 kg (4–6 lbs) per month on orlistat, which equals roughly 0.5–0.75 kg per week — similar to weight loss from diet and exercise alone. The NHS recommends losing no more than 0.5–1 kg per week for sustainable results. Individual weight loss varies significantly depending on your starting weight, diet adherence, physical activity, and metabolism. Orlistat works best as part of a structured weight loss programme alongside dietary changes and increased activity, not as a standalone solution.
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 Rates and NHS Guidance
The NHS recommends losing weight at a rate of 0.5 to 1 kg per week for sustainable, healthy results. This typically requires a calorie deficit of around 500 kcal per day. Orlistat supports this by reducing fat absorption in the digestive system — approximately 30% of dietary fat is not absorbed — but it does not create weight loss on its own without dietary change.
Clinical studies show that people taking orlistat lose an average of 2–3 kg more than with diet and exercise alone over 6 months, though individual results vary considerably. Faster weight loss — over 1.5 kg per week — is not recommended without medical supervision, as it increases the risk of muscle loss, gallstones, and nutritional deficiencies. Use our free BMI calculator to understand your current weight status and set realistic healthy weight goals for your height.
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 Orlistat Results and Individual Factors
Weight loss on orlistat depends on multiple factors beyond the medication itself. Your starting weight, age, metabolism, diet quality, and physical activity level all significantly influence results. Someone losing weight from a higher starting point may see faster initial loss than someone already close to a healthy weight. Orlistat is typically prescribed as part of an NHS weight management programme, which includes dietitian support and behaviour change counselling — these additional components are often more important than the medication alone.
If you're prescribed orlistat, your GP will monitor your progress and adjust your approach if needed. Track your weight loss journey using our free progress tracker to identify patterns and stay motivated over weeks and months, rather than focusing on single-week results.
- 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.
Can I lose 1 kg per week on orlistat?
It's possible but not assured. Orlistat helps reduce fat absorption, but weight loss depends primarily on creating a calorie deficit through diet and exercise. The NHS recommends a sustainable rate of 0.5–1 kg per week. Faster loss is possible but increases health risks. Your GP can advise on realistic targets based on your individual circumstances.
How long does orlistat take to work?
Orlistat begins working immediately by reducing fat absorption, but weight loss typically becomes noticeable within 2–4 weeks as your dietary changes take effect. Most people see meaningful results over months, not weeks. Consistency with diet and activity matters more than the medication alone. It's not a quick-fix solution.
Is orlistat more effective than diet and exercise alone?
Studies show orlistat helps people lose about 2–3 kg more than diet and exercise alone over 6 months. However, the difference is modest. Without dietary changes and increased physical activity, orlistat is ineffective. It's a support tool, not a replacement for lifestyle change.
What if I'm not losing weight on orlistat?
If you're not seeing results after 4–8 weeks, discuss this with your GP. Common reasons include insufficient calorie deficit, not adhering to dietary changes, or medical factors like an underactive thyroid. Your GP may adjust your approach or prescribe a different medication. Use the BMI calculator on this page to track your starting point.
Can I expect to lose weight every single week on orlistat?
No — weight naturally fluctuates week to week due to water retention, hormones, and food timing. It's normal to have weeks with no loss or even small gains despite sticking to your plan. Focus on the trend over 4–8 weeks rather than daily or weekly changes. Progress tracking helps show the real picture 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.