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 the Ketogenic Diet Supports Weight Loss
The ketogenic diet is a low-carbohydrate, high-fat eating approach that may help some people lose weight by shifting the body into ketosis — a metabolic state where fat becomes the primary fuel source. However, weight loss success with keto depends on maintaining a calorie deficit, just like any other diet. In the UK, the ketogenic diet is one of several weight management approaches available, though NHS guidance typically recommends sustainable, balanced approaches. Individual results vary significantly based on personal factors including genetics, adherence, and overall lifestyle. Use our free BMI calculator above to check your current weight status and understand what a healthy weight range looks like for your height.
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.
How the Ketogenic Diet Works for Weight Loss
The ketogenic diet works by severely restricting carbohydrates (typically below 50g per day), which forces the body to enter ketosis. In this state, the liver breaks down fats into ketones, which become the brain and muscles' primary energy source. This metabolic shift may reduce appetite and increase fat burning compared to a standard diet.
- Rapid initial weight loss: Much of the first 1–2 weeks is water loss as glycogen stores deplete. After this, weight loss typically slows to 0.5–1 kg per week — the NHS-recommended safe rate
- Appetite suppression: Ketones may naturally reduce hunger signals, making it easier to maintain a calorie deficit without constantly feeling deprived
- Insulin and blood sugar: Lower carbohydrate intake reduces insulin spikes, which may benefit people with type 2 diabetes or prediabetes
- Calorie deficit remains essential: Keto is not a free-pass diet — weight loss still requires consuming fewer calories than you burn. It simply may be easier to achieve this deficit due to reduced appetite
Try our GLP-1 weight loss calculator to compare how prescription weight loss medication approaches differ from dietary methods alone.
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.
Ketogenic Diet vs Other Weight Management Approaches
In the UK, several weight management approaches are available alongside keto, each with different evidence levels. The ketogenic diet can produce rapid initial results but is challenging to sustain long-term for many people — the restrictive nature means some people find it difficult to stick with. NHS weight loss guidance typically favours more balanced, sustainable dietary changes (Mediterranean diet, portion control) combined with increased physical activity. For adults with a BMI of 30 or above, or 27 or above with weight-related health conditions, prescription weight loss medication is also available through NHS specialist services or private assessment. These medications work alongside lifestyle changes to support weight loss, and individual results vary. Use our weight converter to track your weight in both kg and stone as you progress, and our progress tracker to log changes over time.
- 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 the ketogenic diet safe for long-term weight loss?
The ketogenic diet can be effective short-term, but evidence on long-term safety is mixed. Some people sustain it for years with medical support; others find it difficult to maintain. Potential concerns include nutrient deficiencies, kidney stress in susceptible individuals, and "keto flu" during transition. Always consult your GP before starting, especially if you have diabetes, kidney problems, or take medication.
How quickly will I lose weight on a ketogenic diet?
Initial weight loss is often rapid — 2–5 kg in the first 1–2 weeks — but this is largely water loss. Actual fat loss typically follows the NHS-recommended safe rate of 0.5–1 kg per week. Individual results vary greatly based on starting weight, calorie deficit, and adherence. Expect a plateau as your body adapts.
What's the difference between keto and other low-carb diets?
Ketogenic diet is a specific, strict low-carb approach (under 50g carbs daily) designed to trigger ketosis. Other low-carb diets are less restrictive and may not achieve ketosis. Keto is more restrictive but some people find it produces faster results. The choice depends on your lifestyle and preferences.
Can I use ketogenic diet alongside prescription weight loss medication?
Potentially yes, but this requires careful medical supervision. Combining dietary approaches with medications like GLP-1 injections may increase risk of certain side effects. Always inform your GP or prescriber if you're considering keto while taking weight loss medication. They can assess suitability for your individual situation.
What should I eat on a ketogenic diet for weight loss?
Focus on fatty fish, eggs, full-fat dairy, nuts, seeds, avocados, oils, and low-carb vegetables (spinach, broccoli, cauliflower). Avoid bread, pasta, rice, sugar, and most fruits. Track macros carefully — aim for roughly 70% fat, 25% protein, 5% carbs. Consult a dietitian for personalised guidance, especially long-term.
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.