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
1000 Calorie Deficit Weight Loss — UK Medication Options
A 1000 calorie daily deficit is an aggressive approach that typically results in around 1 kg of weight loss per week, faster than NHS guidelines recommend. While this may be achieved through diet and exercise alone, prescription weight management medication is available in the UK for eligible adults. This guide covers NHS-approved medications, who qualifies, and how to access support through the NHS or private prescribing. Always consult your GP before starting any weight loss programme or medication.
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 Prescription Weight Management Options
Three prescription medications are licensed in the UK for weight management: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). These are GLP-1 receptor agonist injections that work by reducing appetite and supporting fuller feelings after meals. In clinical trials, adults using these medications alongside reduced-calorie diets and increased physical activity achieved weight losses ranging from 14% to 21% of body weight. Eligibility typically requires a BMI of 30 or above, or 27 to 29.9 with weight-related health conditions such as type 2 diabetes, high blood pressure, or sleep apnoea. All three are prescription-only and require clinical assessment before prescribing. You can estimate potential weight loss outcomes using our GLP-1 weight loss calculator, which models results at different medication doses.
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 Specialist Services vs Private Access
NHS access: Available through specialist tier 3 weight management services following GP referral. Availability and waiting times vary significantly by region. Private access: Available through GPhC-registered online pharmacies with UK-licensed prescriber assessments, typically without waiting. Our free BMI calculator helps determine your current category—share this with your GP to start the conversation about prescription weight management. Private costs range from £129–£320 monthly depending on dose. For sustainable results, combine any medication with a structured diet plan, increased physical activity, and behaviour change support. Track your progress using our free progress tracker.
- 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.
Will a 1000 calorie deficit clinically studied weight loss?
A 1000 calorie daily deficit creates conditions for significant weight loss, typically around 1 kg per week alongside exercise and reduced-calorie eating. However, individual results vary based on metabolism, age, activity level, and starting weight. Prescription medications may help, but they work best combined with lifestyle changes, not instead of them.
Is a 1000 calorie deficit safe without medical supervision?
The NHS recommends losing 0.5–1 kg per week, which typically requires a 500 calorie daily deficit. A 1000 calorie deficit is more aggressive and should be attempted only under medical supervision—either through NHS specialist services or private prescriber assessment. Very low calorie diets (under 800 calories) require medical monitoring.
How do Mounjaro and Wegovy support a large calorie deficit?
Both medications reduce appetite and food cravings, making it easier to maintain a reduced-calorie diet. They slow gastric emptying, helping you feel fuller longer. In clinical trials, people using these medications alongside lifestyle changes achieved greater weight loss than diet and exercise alone.
Can my GP refer me for prescription weight loss medication?
Yes, your GP can refer you to a specialist NHS weight management service (tier 3), or you can access private prescribing through an online assessment. Eligibility is based on BMI and weight-related health conditions. Discuss your weight loss goals and options with your GP—they know your full medical history and can advise on the safest approach.
What's the difference between NHS and private weight loss medication?
NHS access is free but involves referral, assessment, and potential waiting lists. Private access is faster but costs £129–£320 monthly. Both require clinical assessment and prescription. The medication and doses are identical; the main difference is pathway and timing. Many people use private options while on NHS waiting lists.
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.