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
Do Probiotics Help With Weight Loss?
Probiotics are living beneficial bacteria that support gut health, but the evidence for direct weight loss is limited and mixed. While some studies suggest certain probiotic strains may support modest improvements in weight management alongside diet changes, they are not considered a primary weight loss tool by the NHS. If you're looking for evidence-based weight management solutions in the UK, prescription medications and lifestyle support are typically more effective options. This guide explores what research shows about probiotics and introduces NHS-approved alternatives for eligible adults.
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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.
Probiotics and Weight Loss — What the Evidence Shows
Probiotics contain live bacteria that may influence gut health and metabolism, but current evidence for weight loss is modest. A 2022 systematic review in the journal Nutrients found that certain probiotic strains showed small effects on body weight and BMI, but results were inconsistent across studies. Most weight loss observed was less than 2 kg over several months, often requiring combined dietary changes and exercise.
- Limited direct effect: Probiotics alone do not produce significant weight loss
- Gut health connection: Improved gut bacteria may support metabolism and digestion, which can indirectly help with weight management
- Strain-specific: Not all probiotics are equal — effects vary by bacterial strain and dosage
- Combined approach: Any weight loss benefit appears only when combined with calorie reduction and physical activity
The NHS does not currently recommend probiotics as a primary weight loss intervention. For UK adults seeking evidence-based weight management, prescription options and lifestyle support have stronger clinical evidence.
Clinically BackedWeight Loss
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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.
Prescription Weight Management Options Available in the UK
If you're looking for effective weight management support in the UK, several prescription-only medications are licensed and available. Mounjaro (tirzepatide) and Wegovy (semaglutide) are GLP-1 receptor agonists that work by reducing appetite and supporting feelings of fullness. Clinical trials showed that Mounjaro helped participants lose an average of 15–21% of body weight, while Wegovy resulted in approximately clinically studied weight loss — though individual results vary significantly.
Eligibility typically requires a BMI of 30 or above, or 27 or above with weight-related health conditions such as type 2 diabetes or high blood pressure. Access is available through NHS specialist weight management services or private prescribing following a clinical assessment with a UK-licensed healthcare professional. Use our free GLP-1 weight loss calculator to explore potential outcomes, and our BMI calculator to check your current classification.
- 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 probiotics effective for weight loss?
Evidence is limited. Some research suggests certain probiotic strains may support modest weight changes when combined with diet and exercise, but effects are typically small (under 2 kg) and inconsistent. Probiotics alone do not produce significant weight loss and the NHS does not recommend them as a primary weight management tool.
What does the NHS recommend for weight loss?
The NHS recommends a structured approach: a calorie deficit of around 500 kcal per day (targeting 0.5–1 kg loss per week), increased physical activity, and dietary changes. For eligible adults, NHS specialist weight management services may prescribe medications like Mounjaro or Wegovy alongside these lifestyle changes.
Who is eligible for prescription weight loss medication in the UK?
Adults with a BMI of 30 or above, or 27 or above with weight-related health conditions (such as type 2 diabetes, high blood pressure, or sleep apnoea), may be eligible. Individual assessment is required. Speak to your GP about referral to a specialist weight management service or contact a private prescriber.
What is the difference between Mounjaro and Wegovy?
Both are GLP-1-based injections taken once weekly. Mounjaro (tirzepatide) is a dual GIP/GLP-1 agonist with average weight loss of 15–21%. Wegovy (semaglutide) is a GLP-1 agonist with average weight loss around 15%. Both require prescription and clinical assessment. Results vary between individuals.
How do I find out if I'm eligible for weight loss support?
Start by calculating your BMI using our free BMI calculator on this page. Then speak to your GP about your options. They can refer you to NHS specialist services (typically tier 3 weight management) or you can seek a private online clinical assessment with a UK-licensed prescriber if you prefer faster 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.