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
Detox and Weight Loss: UK Prescription Medication Options
"Detox" cleanses are often ineffective for lasting weight loss, but prescription weight management medication can help eligible adults lose weight sustainably. The UK has several NHS-licensed options including Mounjaro, Wegovy, and Saxenda — all prescription-only treatments that work alongside diet and exercise. Unlike temporary detox programmes, these evidence-based medications address the biological factors that make weight loss difficult. If you're struggling with your weight, understanding what prescription options are available and who is eligible is an important first step. Calculate your BMI using the free BMI calculator on this page to see where you currently sit on NHS weight categories.
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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 Loss Medications Explained
Three prescription weight loss medications are currently licensed in the UK for eligible adults:
- Mounjaro (tirzepatide) — a once-weekly injection that activates two hormone pathways (GIP and GLP-1). Clinical trials showed average weight loss of 15–21% of body weight over 72 weeks, though individual results vary significantly.
- Wegovy (semaglutide) — a once-weekly GLP-1 injection with average weight loss around 15% of body weight at the maximum dose (2.4 mg). Results are best achieved alongside a reduced-calorie diet and increased physical activity.
- Saxenda (liraglutide) — a daily injection with a lower average weight loss than Mounjaro or Wegovy, typically used when other options are unsuitable.
All three are prescription-only medicines requiring a clinical assessment from a UK-licensed prescriber. Eligibility depends on your BMI and whether you have weight-related health conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease. Try our free GLP-1 weight loss calculator to explore how these medications might work for your weight management plan.
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 Prescription — What's Right for You?
NHS access: Mounjaro and Wegovy are available through NHS specialist tier 3 weight management services. Your GP can refer you if you meet eligibility criteria, but waiting lists vary significantly by region — some areas have lengthy delays. NHS prescribing is cost-free but availability depends on your local integrated care board (ICB).
Private access: Both medications are available through GPhC-registered online pharmacies following an online clinical assessment with a UK-licensed prescriber. This typically has no waiting list, but involves a consultation fee (usually £15–£40) plus the cost of medication (approximately £129–£320 monthly depending on dose). Either route requires a prescription and clinical assessment — weight loss medication is not sold without one.
Speak with your GP about which option suits you best. They can advise on NHS availability in your area and whether you meet eligibility criteria. Use our free BMI calculator and weight converter to gather your health information before your appointment.
- 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 detox really needed before weight loss medication?
No. "Detox" products have no proven benefit for weight loss. Your liver naturally removes toxins. GLP-1 medications like Mounjaro and Wegovy work directly on appetite regulation and do not require pre-treatment with detox products. Start prescription weight loss medication only under medical supervision, not after a detox programme.
Who is eligible for weight loss medication in the UK?
Adults with a BMI of 30 kg/m² or above, or BMI of 27–29.9 with weight-related health conditions (type 2 diabetes, high blood pressure, cardiovascular disease, sleep apnoea). South Asian, Chinese, Black African, and Black Caribbean adults may be eligible at lower BMI thresholds. Your GP or prescriber will assess eligibility individually.
How much weight can I expect to lose with Mounjaro or Wegovy?
Clinical trials showed average weight loss of 15–21% with Mounjaro and around 15% with Wegovy, but individual results vary significantly. Some people lose more, others less. Results are best alongside a reduced-calorie diet and increased physical activity. Use our free GLP-1 weight loss calculator to see projected outcomes based on your starting weight.
Can I get weight loss medication on the NHS?
Yes, Mounjaro and Wegovy are available through NHS specialist weight management services in some areas. Eligibility and availability vary by region. Your GP can refer you if you meet criteria, but waiting times can be several months or longer. Private online prescribing offers faster access but involves consultation and medication costs.
Is prescription weight loss medication safe long-term?
Mounjaro and Wegovy have strong safety data from clinical trials lasting over a year. Common side effects include nausea and digestive changes, which typically improve over time. Serious side effects are rare. You must be monitored by a prescriber during treatment. Always discuss any health concerns with your GP or prescriber before starting.
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.