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 From Keto — UK Health Guide
The ketogenic diet can help some people lose weight by reducing carbohydrate intake and promoting fat metabolism. However, not everyone finds keto sustainable long-term. If you're struggling with weight management in the UK, prescription weight loss medications are also available for eligible adults alongside lifestyle changes like keto or other reduced-calorie diets. This guide covers both dietary approaches and medication options available through the NHS and privately.
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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 Prescription Weight Loss Options
For adults who meet NHS eligibility criteria, three prescription weight loss medications are available in the UK. Mounjaro (tirzepatide) is a once-weekly GLP-1 injection that may help reduce appetite and support feeling fuller. Wegovy (semaglutide) is another once-weekly GLP-1 injection, and Saxenda (liraglutide) is a daily injection. Clinical trials showed average weight losses of 14–21% body weight with these medications, though individual results vary significantly.
You may be eligible if you have a BMI of 30 or above, or 27–29.9 with weight-related health conditions like type 2 diabetes or high blood pressure. South Asian, Chinese, Black African, and Black Caribbean adults may have lower BMI eligibility thresholds. All prescription weight loss medications work best when combined with dietary changes—such as keto or calorie-controlled eating—and increased physical activity. Use our free GLP-1 weight loss calculator to explore potential outcomes at different doses if you think medication might be suitable for you.
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.
NHS vs Private Access and Next Steps
NHS access: Referral to a tier 3 specialist weight management service through your GP. Availability and waiting times vary significantly by region. Private access: Available through GPhC-registered online prescribers following an online clinical assessment, without an NHS referral.
Whether you choose keto, other dietary approaches, or prescription medication, the first step is speaking with your GP. They can assess your individual situation, discuss what might work for you, and refer you to specialist services if appropriate. You can also use our free BMI calculator to understand where you currently stand relative to NHS healthy weight guidelines, which may help guide that conversation.
- 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 use keto alongside prescription weight loss medication?
Yes. Weight loss medications like Mounjaro and Wegovy are typically prescribed alongside reduced-calorie diets and increased physical activity. Keto is a form of calorie reduction, so you could follow it with medical support. Always discuss your dietary approach with your prescriber to ensure it's safe and appropriate for your health profile.
How much weight can I lose with keto?
Weight loss on keto varies. Initial loss may be rapid (partly water weight), followed by slower fat loss. Sustainable loss is typically 0.5–1 kg per week. Long-term results depend on calorie deficit, adherence, individual metabolism, and lifestyle factors. Results are not assured and vary between individuals.
What if keto isn't working for me?
If you've tried keto without sustained results, prescription weight loss medication may be an option. These medications work through different mechanisms than dietary approaches and can be effective for people who find lifestyle changes alone insufficient. Speak with your GP about eligibility.
How do I know if I'm eligible for NHS weight loss medication?
NHS eligibility generally requires a BMI of 30 or above, or 27–29.9 with weight-related health conditions (diabetes, high blood pressure, sleep apnoea, etc.). Speak with your GP, who can assess your individual circumstances and refer you to specialist services if appropriate.
Is prescription weight loss medication available on the NHS?
Yes, NICE has approved tirzepatide (Mounjaro) and semaglutide (Wegovy) for use in NHS specialist weight management services. However, access varies by region and waiting times can be long. Private prescribing is also available through GPhC-registered online providers. Your GP can discuss both options with you.
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.