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
30 Day Weight Loss Challenge — Safe, Evidence-Based Strategies
A 30-day weight loss challenge can be a useful way to kickstart healthier habits and track your progress, but realistic expectations are important. Most UK health guidance recommends losing weight gradually at 0.5–1 kg per week for sustainable results. This means a realistic 30-day target is 2–4 kg, not dramatic transformations. Whether you're starting with diet, exercise, or considering weight management medication through prescription weight loss options, the key to success is consistency and understanding what works for your body. Use our free BMI calculator to establish your starting point, then set evidence-based goals for your challenge.
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.
What's a Realistic 30-Day Weight Loss Target?
The NHS recommends losing weight at a rate of 0.5–1 kg (1–2 lbs) per week for sustainable, healthy results. This means over 30 days, a realistic target is 2–4 kg, depending on your starting weight, diet adherence, and activity level. Faster weight loss is possible but often involves muscle loss alongside fat loss, which isn't ideal for long-term health.
Achieving this typically requires a calorie deficit of around 500 kcal per day, which can be created through a combination of reduced food intake and increased physical activity. A 30-day challenge works best when it focuses on building sustainable habits—such as regular exercise, cooking at home, staying hydrated, and reducing processed foods—rather than extreme restrictions that can't be maintained beyond the month.
- Track your starting weight and BMI using our free weight converter and BMI calculator
- Aim for 150 minutes of moderate activity per week as NHS guidance suggests
- Create a calorie deficit through balanced diet changes, not crash dieting
- Monitor progress weekly rather than daily—weight naturally fluctuates
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.
Using a Structured Approach to Your Challenge
To make your 30-day challenge work, plan specific, measurable targets. Rather than "lose weight", commit to actions like "walk 30 minutes five times a week" or "reduce sugary drinks to two per week". These behavioural changes are more achievable and naturally support weight loss.
If you're interested in weight loss medication support, UK prescription weight loss options such as GLP-1 injections (Mounjaro or Wegovy) are available through NHS specialist services or private prescription after a clinical assessment. Our GLP-1 weight loss calculator can help you explore potential outcomes with medication, though these should always be combined with diet and exercise changes. Keep a progress tracker throughout your 30 days—logging weight, energy levels, and how your clothes fit—rather than relying on scale weight alone, which can mask improvements in body composition.
- 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.
How much weight can I realistically lose in 30 days?
Following NHS guidance of 0.5–1 kg per week, a realistic 30-day target is 2–4 kg. This rate supports sustainable fat loss while preserving muscle. Faster loss is possible but often includes water and muscle loss, making it harder to maintain results long-term.
What's the best diet for a 30-day weight loss challenge?
Rather than a specific diet, focus on creating a moderate calorie deficit (around 500 kcal per day) through balanced, whole foods. Mediterranean-style eating, intermittent fasting, or any approach you can sustain works. Avoid very restrictive diets—they're rarely sustainable beyond 30 days.
Can I use weight loss injections for a 30-day challenge?
Prescription weight loss medications like Mounjaro or Wegovy require ongoing prescription and clinical assessment; they're not designed for short-term use. However, if you're eligible and interested in weight loss medication support for longer-term management, your GP can refer you to NHS specialist services or you can explore private prescription options.
Should I weigh myself daily during the challenge?
Weekly weigh-ins are more useful than daily ones—weight naturally fluctuates due to hydration, digestion, and hormones. Track other markers too: energy levels, how clothes fit, and measurements. Our free progress tracker helps you log all these indicators alongside weight.
What happens after the 30-day challenge ends?
The challenge is most valuable if it builds habits you maintain beyond 30 days. Focus on lifestyle changes rather than temporary restrictions. If you've found success with diet and exercise, consider whether prescription weight management medication might support ongoing progress—always discuss this with your GP first.
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.