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
1 Week Weight Loss Diet Chart: UK Prescription Options
A one-week weight loss diet chart can help structure your eating plan, but sustainable weight management often works best when combined with lifestyle changes. For eligible adults in the UK, prescription weight loss medication alongside dietary adjustments offers additional support. This guide covers UK-licensed medication options, how they work, and whether you might be eligible through the NHS or private prescribing.
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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 Medication Options
Three prescription medications are currently licensed for weight management in the UK:
- Mounjaro (tirzepatide) — a once-weekly injection that activates two natural hunger-regulating pathways (GIP and GLP-1). In clinical trials, it helped participants lose an average of 15–21% of their body weight alongside a reduced-calorie diet.
- Wegovy (semaglutide) — a once-weekly GLP-1 injection. Clinical evidence showed average weight loss of around 15% at the maximum dose.
- Saxenda (liraglutide) — a once-daily GLP-1 injection, typically used when weekly options are unsuitable.
All are prescription-only and require assessment by a licensed prescriber. Eligibility typically includes adults with a BMI of 30 or above, or BMI of 27–29.9 with weight-related health conditions like type 2 diabetes or high blood pressure. Our GLP-1 weight loss calculator can help you explore potential outcomes at different medication doses.
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 vs Private Access: Finding the Right Path
The NHS offers prescription weight loss medication through specialist tier 3 weight management services, though regional availability and waiting times vary significantly across England, Scotland, Wales, and Northern Ireland. Your GP can refer you for assessment, but access depends on local commissioning and existing demand.
Private online prescribing provides faster access without NHS referral — a licensed prescriber reviews your medical history via a consultation and issues a prescription if appropriate. Check your BMI using our free BMI calculator above, then discuss options with your GP or explore private prescribing pathways. The key is combining medication (if eligible) with sustainable dietary changes and physical activity for best results.
- 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 use a one-week diet chart alongside weight loss medication?
Yes. Prescription medications like Mounjaro and Wegovy are designed to work alongside a reduced-calorie diet and physical activity. A structured weekly meal plan can help you stick to calorie targets while medication reduces appetite and cravings. Your prescriber or a dietitian can help tailor this approach to your needs.
What BMI do I need to be eligible for prescription weight loss medication in the UK?
Generally, a BMI of 30 or above qualifies you. If your BMI is 27–29.9, you may still be eligible if you have weight-related health conditions such as type 2 diabetes, high blood pressure, or sleep apnoea. Some UK ethnic groups (South Asian, Chinese, Black African, Black Caribbean) have lower BMI thresholds due to higher health risks at lower weights.
How long does it take to see results with weight loss medication?
Clinical trials showed weight loss begins within the first few weeks for many people, with more significant results visible over 12–16 weeks. However, individual responses vary. Medication works best alongside consistent dietary changes and exercise — there is no assured outcome, and results depend on your personal effort and health circumstances.
How do I access weight loss medication on the NHS in the UK?
Contact your GP and ask for a referral to your local tier 3 specialist weight management service. They will assess your BMI, health history, and eligibility. Availability varies by region (ICB), and waiting times can be several months. Private online prescribing offers faster access if you meet eligibility criteria.
Are there side effects I should know about with weight loss injections?
Common side effects include nausea, diarrhoea, constipation, and reduced appetite — usually temporary as your body adjusts. Serious side effects are rare but include severe stomach pain (possible pancreatitis) and gallbladder complications. Always discuss side effect risks with your prescriber, and seek medical attention if you experience severe symptoms during treatment.
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.