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
6 Week Weight Loss Before And After: What's Realistic with UK Medication?
A realistic 6-week weight loss journey with prescription medication can result in meaningful changes, though individual outcomes vary significantly. In the UK, adults struggling with weight management have access to licensed prescription options like Mounjaro and Wegovy through both NHS and private prescribing. This guide explains what genuine 6-week progress looks like, how prescription weight loss medication works, and how to find out if you're eligible for treatment in the UK.
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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 Prescription Weight Loss Options Available Now
Three prescription medications are currently licensed in the UK for weight management:
- Mounjaro (tirzepatide) — A dual GIP and GLP-1 receptor agonist, starting at 2.5 mg weekly and increasing to a maximum of 15 mg. Clinical trials showed average weight loss of 15–21% of body weight over 72 weeks alongside diet and exercise.
- Wegovy (semaglutide) — A GLP-1 receptor agonist, titrating from 0.25 mg to 2.4 mg weekly. STEP trial data showed approximately 15% average body weight loss at the maximum dose.
- Saxenda (liraglutide) — A daily GLP-1 injection, up to 3 mg, offering similar results to Wegovy.
Over 6 weeks specifically, most people are still in the dose-escalation phase. Significant weight loss typically accelerates after week 8–12 as medication reaches therapeutic doses. Your GP or prescriber will assess your BMI, health conditions, and medical history to determine eligibility and the right medication for you.
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.
Getting Started: NHS vs Private Routes in the UK
NHS Route: Referral to a tier 3 specialist weight management service through your GP. Availability varies by region and waiting times can be lengthy, but treatment is free. Use our free BMI calculator to check where you fall on the NHS weight categories — eligibility typically requires a BMI of 30 or above, or 27–29.9 with weight-related health conditions.
Private Route: Online consultation with a UK-licensed prescriber, prescription issued if appropriate, and dispensing by a registered pharmacy. No NHS referral needed, costs vary by dose and provider (typically £120–£300 monthly). Try our GLP-1 weight loss calculator to explore potential outcomes at different doses and help guide your conversation with a prescriber.
Either way, the first step is speaking with your GP about your weight management goals and exploring what options are right for your health.
- 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 significant weight in 6 weeks with prescription medication?
Weight loss is gradual, especially in the first 6 weeks while doses are being escalated. Most people see modest progress (2–5 kg) in the first month, with acceleration after 6–8 weeks as medication reaches full therapeutic doses. Results vary widely based on starting weight, dose, diet, and exercise. Individual outcomes depend on many factors — always speak to your prescriber about realistic timelines for your situation.
Am I eligible for Mounjaro or Wegovy on the NHS?
NHS eligibility typically requires a BMI of 30 or above, or 27–29.9 with weight-related health conditions like type 2 diabetes, high blood pressure, or sleep apnoea. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds apply. Contact your GP for a referral to your local specialist weight management service. Availability varies significantly by region.
What happens if I don't see results in 6 weeks?
This is normal — most people are still titrating medication doses at 6 weeks. Weight loss accelerates as doses increase. If you're on maximum therapeutic dose and not seeing progress after 12 weeks, discuss with your prescriber about potential adjustments, adherence to diet and exercise, or whether the medication is right for you. Some people may respond better to a different medication.
Will weight come back after stopping prescription medication?
Weight regain can occur if diet and exercise habits don't change. Prescription medications work best alongside sustainable lifestyle changes. Long-term outcomes depend on maintaining reduced-calorie eating and regular physical activity. Track your progress using our free progress tracker to monitor both medication and lifestyle impact.
How much does private weight loss medication cost in the UK?
Costs vary by provider and dose. Mounjaro and Wegovy typically range from £120 to £320 per month depending on the specific dose you're prescribed. NHS treatment is free but may involve waiting lists. Discuss costs with your prescriber — some providers offer dose-based pricing or subscription plans.
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.