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
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2 Week Weight Loss Program with UK Prescription Medication
A structured 2 week weight loss program in the UK can be accelerated with prescription medication if you're eligible. While most sustainable weight loss takes several months, prescription options like Mounjaro and Wegovy are available through NHS specialist services or private prescribing for adults with a BMI of 30 or above, or 27 or above with weight-related health conditions. This guide explains your options and how to find out if you qualify for medication-supported weight management 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
Three prescription-only medications are currently licensed in the UK specifically for weight management:
- Mounjaro (tirzepatide) — a dual GIP and GLP-1 receptor agonist administered once weekly. In clinical trials, participants lost an average of 15–21% of their body weight, though individual results vary significantly.
- Wegovy (semaglutide) — a GLP-1 receptor agonist, also once weekly. Clinical evidence shows average weight loss of approximately 15% of body weight alongside a reduced-calorie diet and increased physical activity.
- Saxenda (liraglutide) — a GLP-1 injection administered daily, with similar efficacy to Wegovy but requiring daily rather than weekly dosing.
All three medications work by helping regulate appetite and supporting feelings of fullness, making it easier to maintain a reduced-calorie diet. Each requires a prescription following a clinical assessment to confirm eligibility and suitability. Use our free GLP-1 weight loss calculator to explore potential outcomes at different doses if you're considering medication-supported weight management.
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 Prescribing in the UK
Access to prescription weight loss medication in the UK differs significantly depending on your route:
NHS route: Referral to a tier 3 or tier 4 specialist weight management service through your GP. NICE has approved tirzepatide (Mounjaro) and semaglutide (Wegovy) for NHS use, but availability varies by region and waiting lists can be lengthy.
Private route: Available through UK-licensed prescribers following an online clinical assessment. No NHS referral needed, though costs apply (typically £130–£320 monthly depending on dose).
Your GP can assess your BMI using our free BMI calculator and discuss whether you meet eligibility criteria. Even if pursuing private medication, your GP should be informed of any weight loss treatment you're using.
- 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 weight in 2 weeks with prescription medication?
Prescription weight loss medications like Mounjaro and Wegovy may help you lose weight within 2 weeks, though initial weight loss is often modest (typically 1–2kg in the first week). Significant, sustainable weight loss develops over weeks and months. These medications are designed for long-term weight management alongside lifestyle changes, not rapid short-term results.
How do I know if I'm eligible for prescription weight loss medication in the UK?
You may be eligible if you have a BMI of 30 or above, or a BMI of 27–29.9 with weight-related health conditions like type 2 diabetes, high blood pressure, or cardiovascular disease. Adults of South Asian, Chinese, Black African, or Black Caribbean heritage may be eligible at lower BMI thresholds. Your GP can assess your eligibility.
What's the difference between NHS and private weight loss medication access?
NHS access requires referral to a specialist weight management service with potential waiting lists. Private access is available through online prescribers without NHS referral but involves out-of-pocket costs. Both require a valid prescription from a UK-licensed prescriber based on clinical assessment.
Do I need to change my diet and exercise while taking weight loss medication?
Yes, prescription weight loss medications work most effectively alongside a reduced-calorie diet and increased physical activity. These medications support but do not replace lifestyle changes. Your prescriber will provide guidance on diet and exercise alongside medication.
Can my GP prescribe Mounjaro or Wegovy?
Your GP can refer you to specialist services for assessment and potential prescription. However, initial prescribing is typically done through tier 3 specialist weight management services on the NHS. Private online prescribers can also issue prescriptions if you meet clinical criteria and prefer private access.
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.