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
Diet Pop and Weight Loss — What You Need to Know
Diet pop and other low-calorie soft drinks are often marketed as weight loss aids, but the evidence is mixed. While diet versions contain fewer calories than regular pop, artificial sweeteners and drinking habits matter more than the drink itself. If you're struggling with weight loss, prescription medications like Mounjaro and Wegovy are now available in the UK for eligible adults. These GLP-1 and dual-action injections may help support weight management alongside lifestyle changes. This guide explains your options and how to find out if you're eligible.
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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 Prescription Weight Loss Medications — What's Available
Three prescription medications are currently licensed in the UK for weight management:
- Mounjaro (tirzepatide) — a once-weekly injection that activates dual GIP and GLP-1 hormone pathways. In clinical trials, participants lost an average of 15–21% of their body weight over 72 weeks alongside diet and exercise.
- Wegovy (semaglutide) — a once-weekly GLP-1 injection. Clinical trials showed average weight loss of approximately 15% at 68 weeks.
- Saxenda (liraglutide) — a daily GLP-1 injection, the longest-established option in the UK.
You are eligible if you have 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 may apply. All are prescription-only and require clinical assessment before being prescribed. Use our free BMI calculator to check where you stand, and our GLP-1 weight loss calculator to estimate potential outcomes at different 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 — How to Get Support
NHS route: Ask your GP for a referral to a tier 3 specialist weight management service. Availability varies significantly by region, and waiting times can be several months. Some areas have limited access to newer medications.
Private route: Online consultations with UK-licensed prescribers are available without NHS referral. A private assessment costs £30–£150, and monthly medication costs range from £129–£320 depending on dose. Neither route assures prescription — eligibility is assessed individually.
Next step: Book a GP appointment to discuss your weight management goals. They can refer you to NHS services if appropriate, or advise on private options. Track your current weight and BMI using our free weight converter and progress tracker to prepare for the conversation.
- 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.
Will diet pop help me lose weight?
Diet pop contains zero sugar and minimal calories, so it won't directly cause weight gain. However, artificial sweeteners don't reduce appetite the way whole foods do, and some research suggests they may maintain sweet cravings. For weight loss, focus on total calorie intake, water intake, and physical activity rather than relying on diet drinks alone.
What's the difference between Mounjaro and Wegovy?
Both are once-weekly injections for weight management. Mounjaro uses a dual GIP+GLP-1 mechanism and may produce slightly higher average weight loss (15–21% vs 15%). Wegovy activates GLP-1 only. Both are prescription-only and require clinical assessment. Your prescriber will recommend the most suitable option based on your health profile.
Am I eligible for prescription weight loss medication on the NHS?
You may be eligible if your BMI is 30 or above, or 27–29.9 with weight-related health conditions (type 2 diabetes, high blood pressure, obstructive sleep apnoea, or cardiovascular disease). For South Asian, Chinese, Black African, or Black Caribbean adults, lower thresholds apply. Ask your GP for an assessment or referral to specialist weight management services.
How quickly will I lose weight on Mounjaro or Wegovy?
Clinical trials showed average weight loss of 0.5–1 kg per week, though individual results vary significantly. Weight loss typically begins within 2–4 weeks and continues over several months. Results depend on dose, adherence, diet, and exercise. Faster loss isn't necessarily healthier — the NHS recommends sustainable weight loss of 0.5–1 kg per week.
Can I get Mounjaro or Wegovy privately without waiting for the NHS?
Yes. UK-licensed online prescribers assess eligibility and issue prescriptions if clinically appropriate. Private prescriptions are dispensed by GPhC-registered pharmacies. Costs vary, but budget £30–£150 for assessment and £129–£320 per month for medication, depending on dose. It bypasses NHS waiting lists but is not funded by the NHS.
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.