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 Is T5 Weight Loss and How Does It Work?
T5 typically refers to thyroid-based weight loss or fat-burning tablets containing stimulants — though the term is often used loosely in online discussions about gradual weight management methods. If you're exploring weight management in the UK, it's important to understand safe, evidence-based options. The NHS recommends losing weight at a rate of 0.5 to 1 kg per week through sustainable lifestyle changes. Our free BMI calculator can help you understand your current weight status, and our GLP-1 weight loss calculator can show you potential results with prescription weight loss medication if you're eligible.
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 Weight Loss and Prescription Options in the UK
T5 and similar unregulated products are not recommended by the NHS because they often contain undisclosed stimulants, have unpredictable side effects, and lack clinical evidence. Instead, if you're looking for weight management support in the UK, consider these evidence-based approaches:
- Lifestyle changes: A calorie deficit of around 500 kcal per day typically results in approximately 0.5 kg per week loss, alongside increased physical activity
- NHS weight loss support: Your GP can refer you to tier 3 weight management services offering behaviour change programmes and dietary guidance
- Prescription weight loss medication: If you have a BMI of 30 or above (or 27+ with weight-related health conditions such as type 2 diabetes or high blood pressure), you may be eligible for prescription weight loss injections like Wegovy or Mounjaro following clinical assessment
- Referral pathways: Access through NHS specialist services (which may have waiting lists) or private online prescribing after consultation with a UK-licensed prescriber
Our GLP-1 weight loss calculator can help you explore potential results with licensed prescription medication, though individual results always vary.
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.
Why Prescription Weight Loss Is More Reliable
Licensed weight loss medications like Wegovy (semaglutide) and Mounjaro (tirzepatide) have been tested in large clinical trials and are approved by the MHRA for use in the UK. Wegovy showed average weight loss of approximately 15% body weight in the STEP-1 trial, whilst Mounjaro demonstrated 15–21% average loss depending on dose — results that come alongside structured clinical monitoring and safety oversight.
Unregulated products sold online typically lack this evidence, safety data, and prescriber oversight. If you're considering weight loss medication, speak with your GP or a licensed prescriber who can assess your individual health status, review potential side effects, check for drug interactions, and determine eligibility. This personalised approach is far safer than unregulated alternatives.
- 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.
Is T5 weight loss safe to use?
T5 products are not regulated by the MHRA and their contents are often undisclosed. They frequently contain undeclared stimulants which carry cardiovascular and other health risks. The NHS does not recommend these products. If you're seeking weight loss support, speak with your GP about evidence-based options or prescription medications.
What's the difference between T5 and prescription weight loss medication?
T5 products are unregulated and unproven. Prescription weight loss medications like Wegovy and Mounjaro are MHRA-approved, clinically tested, and monitored by healthcare professionals. They have established safety profiles, documented side effects, and require clinical assessment before prescribing.
How much weight can I expect to lose with safe weight loss methods?
The NHS recommends losing 0.5–1 kg per week through lifestyle changes (diet and exercise). With prescription weight loss medication alongside lifestyle changes, clinical trials show average losses of 15–21% body weight. Individual results always vary, and a prescriber can discuss realistic expectations for your situation.
Can my GP prescribe weight loss medication on the NHS?
Access to prescription weight loss medication on the NHS is through specialist tier 3 weight management services, not standard GP prescription. You'll need a referral from your GP and eligibility assessment. Availability varies significantly by region. Private online prescribing is also available after consultation with a UK-licensed prescriber.
What should I do if I want to lose weight safely in the UK?
Start by speaking with your GP who can assess your health, discuss your goals, and advise on the best approach for you. You can use our free BMI calculator to understand your current status. The NHS Weight Loss Plan offers free digital support, and if eligible, your GP can refer you to specialist services or discuss prescription options.
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.