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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Weight Loss Vitamins — What the Evidence Shows
Weight loss vitamins and supplements are often marketed as solutions for shedding pounds, but the evidence is more nuanced than many believe. While certain nutrients play important roles in metabolism and weight management, vitamins alone are not typically sufficient for sustainable weight loss in the UK. Most effective weight management combines adequate nutrition, physical activity, and sometimes prescription medication alongside a reduced-calorie diet. This guide explains which vitamins and nutrients may genuinely support your weight management journey, and what the evidence actually says about their effectiveness.
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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.
Which Vitamins May Support Weight Management?
Several vitamins and minerals play roles in metabolism and energy regulation, though their direct impact on weight loss is often limited:
- Vitamin D: Low vitamin D levels are linked to obesity and metabolic issues in UK population studies. Adequate vitamin D (10–25 micrograms daily) supports calcium absorption and immune function.
- B vitamins (B12, B6, B3): These support energy metabolism and nervous system function, but taking extra B vitamins beyond dietary intake does not significantly accelerate weight loss.
- Iron: Deficiency can reduce energy levels and exercise capacity, limiting weight management efforts.
- Magnesium: Involved in muscle function and blood sugar regulation, though supplementation shows modest effects on weight loss.
Rather than expensive supplements, most NHS guidance emphasizes meeting vitamin and mineral needs through balanced whole foods. For weight management, our BMI calculator can help you understand your current health position, and your GP can advise on whether specific supplement testing is warranted based on your diet and health history.
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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.
Vitamins vs. Prescription Weight Loss Medication
If you're exploring nhs weight loss options or considering prescription weight loss medication, it's important to understand that vitamins function differently than evidence-based treatments. Unlike vitamins, prescription weight loss medications such as GLP-1 injections have undergone rigorous clinical trials demonstrating measurable weight loss. Prescription weight loss uk services work by affecting appetite regulation and metabolism directly, not by providing micronutrients.
For lose weight uk approaches that have proven effectiveness, your GP can discuss whether you're eligible for prescription weight loss medication or referral to a weight management service. In the meantime, focus on adequate hydration, balanced nutrition with whole foods, and regular physical activity. Track your progress using our free progress tracker to monitor what actually works for your body over time.
- 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.
Do weight loss vitamins actually work?
Most individual vitamins do not produce significant weight loss on their own. While certain nutrients support metabolism (B vitamins, vitamin D, magnesium), you cannot "supplement" your way to sustainable weight loss. Weight management requires a calorie deficit, physical activity, and adequate overall nutrition. Your GP can check for specific deficiencies if needed.
Is vitamin D important for weight management?
Yes — low vitamin D is linked to higher obesity risk and metabolic issues. UK adults should aim for 10–25 micrograms daily, especially during autumn and winter. However, vitamin D supplementation alone does not cause weight loss; it supports general health and may improve energy levels for exercise.
Should I take supplements while using weight loss medication?
This depends on your specific medications and health status. If you're prescribed GLP-1 weight loss medication, inform your prescriber about all supplements you take, as some may interact or affect medication absorption. Your GP or prescriber can advise on what is safe and beneficial alongside your treatment.
What's the best way to get vitamins for weight loss?
Whole foods are superior to supplements for weight management. Focus on nutrient-dense foods: lean proteins, vegetables, fruits, whole grains, and healthy fats. These provide vitamins, minerals, and fibre while supporting satiety and stable blood sugar — all essential for sustainable weight loss.
Can I use vitamins instead of changing my diet and exercise?
No. Weight loss requires a calorie deficit and increased physical activity — vitamins cannot replace these fundamentals. If you've struggled with traditional approaches, discuss bmi weight loss options and prescription medications with your GP. Our GLP-1 weight loss calculator can help you explore what evidence-based treatments might achieve.
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.