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
Meal Replacements For Weight Loss In The UK
Meal replacement shakes and diet products are popular for weight loss, but evidence shows that prescription weight management options are increasingly available to eligible UK adults. If you're considering weight loss support, it's worth understanding both commercial meal replacements and NHS-approved medication options that may be more effective for significant, sustained weight loss. Your GP can help you choose the right approach based on your individual health needs.
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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.
Prescription Weight Loss Options Available In The UK
For adults struggling with weight management, the UK now offers several prescription-only weight loss medications that have shown stronger clinical evidence than meal replacements alone. These include Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). Mounjaro is a dual GIP and GLP-1 receptor agonist—clinical trials showed participants lost an average of 15–21% of their body weight over 72 weeks, making it the most effective option currently licensed in the UK. Wegovy, a GLP-1 agonist, showed average weight loss of around 15% in clinical trials. Saxenda is a once-daily GLP-1 injection option.
All three medications work by reducing appetite, helping you feel fuller after smaller meals, and supporting sustained weight loss when combined with a reduced-calorie diet. Unlike meal replacements, which are temporary food swaps, prescription medications address the hormonal factors underlying excess weight. Use our GLP-1 weight loss calculator to explore potential results 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 Eligibility And How To Access Weight Loss Support
In the UK, you may be eligible for prescription weight loss medication through the NHS if you have a BMI of 30 or above (or BMI 27–29.9 with weight-related health conditions like type 2 diabetes, hypertension, or cardiovascular disease). For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds apply due to higher health risks at lower weights.
Access is typically through NHS specialist tier 3 weight management services—your GP can refer you. However, waiting lists vary significantly by region. You can also explore prescription weight loss through private online prescribing, which offers faster access without an NHS referral. Check your personal eligibility using our free BMI calculator above, then discuss options with your GP to decide the best approach for your situation.
- 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.
Are meal replacements effective for long-term weight loss?
Meal replacements can support short-term weight loss through calorie reduction, typically achieving 0.5–1 kg per week. However, long-term results are modest—many people regain weight once returning to normal eating. Research shows that prescription weight loss medications produce significantly better sustained results, especially for people with a BMI over 30.
What's the difference between meal replacements and prescription weight loss medication?
Meal replacements reduce calories by replacing meals with shakes or bars. Prescription medications like Mounjaro and Wegovy work by reducing appetite hormones, helping you eat less naturally without relying on food swaps. Combined with lifestyle changes, they produce stronger, more sustained weight loss than meal replacements alone.
Can I get prescription weight loss medication on the NHS?
Yes, if you're eligible. NHS access is through specialist weight management services (tier 3)—your GP can refer you. Eligibility requires a BMI of 30 or above, or 27–29.9 with weight-related health conditions. Waiting times vary by region. Private prescribing offers faster access without NHS referral.
How much weight can I expect to lose with prescription medication?
In clinical trials, participants lost an average of 15–21% of their body weight with Mounjaro over 72 weeks, and around 15% with Wegovy. Individual results vary significantly and depend on dose, adherence, diet, and physical activity. Use our GLP-1 weight loss calculator to estimate potential outcomes based on your starting weight.
What should I do first—try meal replacements or speak to my GP about medication?
If you have a BMI over 30 or weight-related health conditions, speak to your GP—you may be eligible for prescription support. If you're not yet eligible or prefer to start with lifestyle changes, meal replacements can help achieve a calorie deficit. However, prescription medication often produces better long-term results with medical support and monitoring.
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.