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
Steroids for Weight Loss — What Actually Works in the UK
Anabolic steroids are not used for weight loss in the UK, and using them for this purpose is both dangerous and illegal without a prescription. If you're looking for evidence-based weight management options, the NHS and licensed prescribers offer prescription medications specifically designed for weight loss. These are GLP-1 receptor agonists — a completely different class of medicine — and they're available to eligible UK adults through NHS specialist services or private prescribing.
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 Weight Management Medications
The UK has approved three prescription medications specifically for weight management in adults. Mounjaro (tirzepatide) is a once-weekly injection that activates both GIP and GLP-1 hormone pathways, and clinical trials showed average weight loss of around 15–21% of body weight. Wegovy (semaglutide) is also a once-weekly injection using a single GLP-1 mechanism, with clinical trial results showing approximately 15% average weight loss. Saxenda (liraglutide) is a daily injection option, also GLP-1-based.
All three are prescription-only medicines requiring a clinical assessment before prescription. Individual results vary significantly depending on dose, lifestyle changes, and personal response. You can use our free GLP-1 weight loss calculator to explore potential outcomes at different doses, and our BMI calculator to check where you currently stand against NHS weight categories.
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 Access vs Private — How to Find Out if You're Eligible
NHS route: Weight management medications are available through specialist tier 3 services, typically after referral from your GP. Eligibility generally requires a BMI of 30 or above, or 27–29.9 with weight-related health conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease. South Asian, Chinese, Black African, and Black Caribbean adults may qualify at lower BMI thresholds.
Private route: Available through UK-licensed online prescribers following a clinical assessment, without needing an NHS referral. This option is typically faster but involves out-of-pocket costs.
Your GP can discuss which route suits you and assess your eligibility based on your individual health profile and weight loss goals.
- 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.
Why aren't steroids used for weight loss in the UK?
Anabolic steroids are not approved for weight loss. They carry serious health risks including liver damage, cardiovascular problems, and hormonal imbalances. Modern weight management uses GLP-1 medicines like Mounjaro and Wegovy, which work through natural hormone pathways and are evidence-based and safe when prescribed appropriately.
What's the difference between GLP-1 medications and steroids?
GLP-1 medications mimic natural hormones that regulate appetite and blood sugar. Anabolic steroids are synthetic testosterone used to build muscle, not lose fat. GLP-1 medicines are prescribed for weight loss; steroids are not. They work by completely different mechanisms and carry different risks.
How quickly can I expect weight loss with prescription medications?
Weight loss typically becomes noticeable after 2–4 weeks at therapeutic doses. Clinical trials showed average losses of 15–21% over 68–72 weeks alongside reduced-calorie diet and increased physical activity. Your GLP-1 calculator can project potential outcomes. Weight loss rate varies significantly between individuals.
Am I eligible for NHS weight loss medication?
You may be eligible if you have a BMI of 30 or above, or 27–29.9 with weight-related conditions like type 2 diabetes or high blood pressure. Lower thresholds apply for certain ethnic backgrounds. Your GP can assess your individual eligibility and refer you to specialist services if appropriate.
What if I don't qualify for NHS weight loss medication?
You could discuss private prescribing options with a UK-licensed online prescriber, explore tier 2 NHS weight management programmes with your GP, or focus on lifestyle changes including reduced-calorie diet and increased physical activity. Your GP can guide you toward the most appropriate option for your situation.
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.