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
Keto Diet and Weight Loss in the UK
The ketogenic diet is a low-carbohydrate, high-fat eating approach that many people use for weight management in the UK. Whilst dietary approaches like keto can support weight loss, prescription medications are also available for eligible adults seeking additional support. This guide covers how keto works, UK weight management options, and how prescription weight loss medication might fit into your health goals. Our free BMI calculator can help you understand your current weight status and eligibility for treatment options.
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.
Prescription Weight Loss Medication Available in the UK
If you're considering weight management support beyond dietary changes, three prescription medications are currently licensed in the UK for weight loss in eligible adults:
- Mounjaro (tirzepatide) — a dual GIP and GLP-1 receptor agonist given as a once-weekly injection, with clinical trials showing average weight loss of 15–21% of body weight
- Wegovy (semaglutide) — a GLP-1 receptor agonist once-weekly injection, with evidence showing approximately 15% average body weight loss
- Saxenda (liraglutide) — a GLP-1 receptor agonist given as a daily injection
You may be eligible if you have a BMI of 30 or above, or BMI of 27–29.9 with weight-related health conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease. Use our free GLP-1 weight loss calculator to explore potential outcomes with prescription medication. Individual results vary significantly, and these medications work best alongside dietary changes and increased physical activity.
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.
Getting Prescription Weight Loss Treatment in the UK
Access to prescription weight loss medication in the UK comes through two main routes: NHS specialist services or private prescribing. Through the NHS, your GP can refer you to a specialist tier 3 weight management service, though waiting lists vary significantly by region. Private access is available through online consultations with UK-licensed prescribers who assess your eligibility following a clinical assessment. Your GP can advise which option suits your circumstances. Whichever route you choose, prescription weight loss medication is typically used alongside lifestyle changes like dietary modifications and increased exercise — not as a replacement for them. Track your progress using our free progress tracker once you've started your weight management journey.
- 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.
Does the keto diet work better than prescription weight loss medication?
Both can be effective for weight management. Keto supports some people through appetite control via low carbs; prescription GLP-1 medications work by mimicking natural appetite-regulating hormones. Many people combine dietary approaches with medication for better results. Individual responses vary significantly. Your GP can help you decide what suits you best.
Who is eligible for prescription weight loss medication in the UK?
Adults with a BMI of 30 or above, or BMI of 27–29.9 with weight-related health conditions (diabetes, high blood pressure, heart disease) may be eligible. Some ethnic groups have lower thresholds due to higher health risks at lower BMI. A prescriber will assess your individual eligibility following a clinical consultation.
Can I get Mounjaro or Wegovy on the NHS?
Yes, tirzepatide (Mounjaro) and semaglutide (Wegovy) are available through NHS specialist weight management services, though regional availability and waiting times vary considerably. Your GP can refer you to your local tier 3 service. Private access is also available through online prescribing if NHS routes aren't accessible.
How much weight can I expect to lose with prescription medication?
Clinical trials show average weight loss of 15–21% of body weight with Mounjaro and approximately 15% with Wegovy, achieved alongside reduced-calorie diet and increased activity. However, individual results vary significantly. Some people lose more, some less. A prescriber can discuss realistic expectations for you specifically.
Can I combine keto diet with prescription weight loss injections?
Yes, many people combine dietary approaches like keto with prescription medication for additional support. However, very low-carbohydrate diets combined with GLP-1 medications may require monitoring for side effects like nausea or electrolyte changes. Always discuss your diet plan with your prescriber before starting medication.
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.