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
Five Week Weight Loss — What You Can Realistically Achieve
Losing weight in five weeks is possible, but realistic expectations matter. The NHS recommends losing 0.5 to 1 kg per week for sustainable results — meaning five weeks could see a loss of 2.5 to 5 kg if you follow evidence-based approaches. Weight loss depends on your starting point, calorie deficit, activity level, and individual metabolism. This guide explains what's achievable in five weeks, how to track progress safely, and when prescription weight loss medication might be considered as part of a wider weight management plan in the UK.
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.
Safe and Realistic Five Week Weight Loss
To lose weight consistently over five weeks, you need a calorie deficit of around 500 kcal per day, which typically results in losing approximately 0.5 kg per week. Over five weeks, this equals 2.5 kg. A larger deficit of 1000 kcal per day can support 1 kg per week loss, totalling 5 kg in five weeks — though this requires medical supervision if sustained long-term.
- Calorie deficit approach: Track food intake using an app or food diary to identify where to reduce calories without deprivation
- Increased activity: Adding 30 minutes of moderate exercise most days supports additional calorie burn
- Dietary changes: NHS weight management UK guidance recommends whole foods, vegetables, lean proteins, and reduced sugar — not rapid restriction
- Hydration and sleep: Drinking water and getting 7–9 hours sleep support metabolism and reduce cravings
Use our free BMI calculator above to establish your starting point, then track progress weekly to stay motivated without obsessing over short-term fluctuations.
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.
When Prescription Weight Loss Might Be Considered
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, prescription weight loss medication may be an option. GLP-1 weight loss injections like Wegovy (semaglutide) or Mounjaro (tirzepatide) work by reducing appetite and helping you feel fuller after smaller meals. Clinical trials showed Wegovy users lost around 15% of body weight over several months — but these medications are prescription-only and require clinical assessment by your GP or a licensed prescriber.
Our GLP-1 weight loss calculator can help estimate potential outcomes at different doses. Any medication approach must be combined with dietary changes and increased physical activity to be effective. Five weeks is a short timeframe — sustainable weight management typically shows results over months, not days.
- 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 lose 1 stone in five weeks?
Losing 1 stone (6.35 kg) in five weeks requires a very large calorie deficit and is not recommended by the NHS. Safe loss is 0.5–1 kg per week, meaning 5 weeks could realistically achieve 2.5–5 kg. gradual weight management often leads to muscle loss and is difficult to sustain.
What's the fastest safe way to lose weight in five weeks?
Combine a moderate calorie deficit (500–750 kcal daily) with regular exercise and whole foods. Expect 2.5–3.75 kg loss. Avoid very low calorie diets without medical supervision. Use our weight converter to track progress between kg and stone.
Do weight loss injections work in five weeks?
Prescription medications like Wegovy take time to work — most users see noticeable loss after 4–8 weeks. Five weeks is early in treatment. Injections are prescribed alongside diet and exercise, and results vary between individuals.
Should I see my GP before trying to lose weight in five weeks?
Yes, it's good practice. Your GP can assess your health, rule out underlying conditions affecting weight, and suggest safe approaches. If you're considering prescription medication, your GP or a licensed prescriber must assess your eligibility.
What if I don't lose weight in five weeks?
Weight loss isn't linear — some weeks show no change despite following a plan. This is normal. Focus on habit changes rather than the scales. If you're not seeing progress after 8–12 weeks of consistent effort, speak to your GP about barriers or whether medication support might help.
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.