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
What Helps With Weight Loss?
Weight loss is achieved through a combination of approaches tailored to your individual needs and health. Whether you're looking to lose weight in the UK through lifestyle changes, dietary adjustments, or with medical support, understanding your options is the first step. The NHS recommends a multi-faceted approach combining reduced calorie intake, increased physical activity, and behavioural changes — and for some people, prescription weight loss medication may also help. Our free BMI calculator can help you understand your current weight status and set realistic goals for your health.
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.
Evidence-Based Weight Loss Methods
Dietary approaches form the foundation of sustainable weight loss. A calorie deficit of approximately 500 kcal per day typically results in weight loss of around 0.5 kg per week — the NHS-recommended safe rate. Popular evidence-based diets include the Mediterranean diet (strong cardiovascular benefits), intermittent fasting (16:8 or 5:2 patterns), and low-carbohydrate approaches, though research shows long-term outcomes are similar across methods when calories are controlled.
Physical activity supports weight loss by increasing calorie burn, preserving muscle mass, and improving metabolic health. The NHS recommends 150 minutes of moderate aerobic activity weekly plus strength training twice weekly. Even modest increases in daily movement — walking, cycling, or climbing stairs — contribute meaningfully to weight management UK outcomes.
Behavioural support through structured programmes, apps, or group support (like NHS Weight Loss Plan) helps sustain changes long-term. Research consistently shows that people who track their progress and have accountability lose more weight than those attempting change alone.
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.
Prescription Weight Loss Medication — When It Helps
For some people, prescription weight loss medication may help alongside lifestyle changes. GLP-1 weight loss injections like Wegovy (semaglutide) and Mounjaro (tirzepatide) are licensed in the UK for adults with a BMI of 30 or above, or 27 or above with weight-related health conditions. Clinical trials show these medications may help participants lose an average of 15–21% of their body weight — though individual results vary significantly.
Our GLP-1 weight loss calculator can help you estimate potential outcomes at different doses. Access to prescription weight loss medication in the UK is through NHS specialist weight management services or private clinical assessment. Your GP or prescriber will assess whether this approach is suitable for your individual health situation.
- 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.
What's the fastest safe rate of weight loss?
The NHS recommends losing 0.5–1 kg (1–2 lbs) per week for sustainable results. Faster weight loss is possible with medical support but increases the risk of muscle loss and nutritional deficiencies. Very rapid loss should only be undertaken under medical supervision.
Which diet is best for weight loss?
Research shows that the "best" diet is the one you can sustain long-term. Mediterranean, intermittent fasting, low-carbohydrate, and calorie-restriction approaches all work — the key is maintaining a calorie deficit. Consistency matters more than the specific diet chosen.
How much does physical activity matter for weight loss?
Physical activity is most effective when combined with dietary changes. Exercise alone without calorie reduction typically produces modest weight loss, but it preserves muscle mass, improves cardiovascular health, and supports long-term weight management. Aim for 150 minutes of moderate activity weekly.
Can GLP-1 injections help me lose weight?
GLP-1 medications like Wegovy are licensed in the UK and evidence suggests they may help reduce appetite and support weight loss when combined with diet and exercise. Clinical trials showed average weight loss of around 15% body weight. Individual results vary, and prescription is based on clinical assessment.
How do I access weight loss support on the NHS?
Start by speaking with your GP, who can refer you to NHS Tier 3 specialist weight management services. These offer structured programmes, behaviour change support, and access to prescription medication where appropriate. Availability and waiting times vary by region.
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.