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 Vitamins Really Help With Weight Loss?
Vitamins alone cannot cause weight loss, but certain deficiencies may slow your metabolism and make weight management harder. If you're exploring weight loss options in the UK, understanding which vitamins support healthy weight management — and which claims are overhyped — is important. This guide covers the evidence, which vitamins matter most, and how they fit into a balanced weight management plan alongside diet, physical activity, and where appropriate, prescription weight loss medication. Most people can get the vitamins they need from food, but supplementation may help in specific cases. Your GP can advise whether you need vitamin testing or supplements as part of your personal weight management strategy.
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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 Are Linked to Weight Management?
Several vitamins play roles in metabolism and appetite regulation. Vitamin D deficiency is linked to higher body weight and increased diabetes risk — many UK adults are deficient, especially in winter months. B vitamins (especially B12 and folate) support energy metabolism, though taking extra B vitamins won't create weight loss without a calorie deficit. Iron is essential for thyroid function and oxygen transport; low iron can slow metabolism. Calcium may support bone health during weight loss but doesn't directly cause weight loss.
However, taking vitamin supplements without addressing calorie intake, physical activity, and underlying health conditions will not lead to sustainable weight loss. If you have weight management concerns in the UK, using our free BMI calculator can help you understand your current weight status, and your GP can assess whether vitamin deficiencies are contributing factors in your case.
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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.
Vitamin Supplements vs. Real Weight Loss Solutions
Weight loss requires a calorie deficit — this is the fundamental principle. No vitamin supplement creates weight loss alone. Some supplement companies make misleading claims about "metabolism-boosting" vitamins; the evidence for most such claims is weak or absent. The NHS recommends focusing on sustainable lifestyle changes: reduced-calorie diet, increased physical activity, and good sleep.
For individuals with a BMI of 30 or above (or 27+ with weight-related health conditions), prescription weight loss options — including GLP-1 injections like Mounjaro or Wegovy — are available through NHS specialist services or private prescription. These work alongside diet and exercise. Our GLP-1 weight loss calculator can help you explore potential outcomes. Always speak with your GP or a healthcare professional before starting any supplement or medication.
- 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 vitamin B12 supplements help you lose weight?
B12 supports energy metabolism, but taking B12 supplements won't cause weight loss unless you have a genuine deficiency. High-dose B12 injections marketed for "weight loss" lack strong evidence. If your GP suspects B12 deficiency (more common in vegans, those with digestive conditions, or over 50s), supplementation is medically appropriate — but weight loss still requires a calorie deficit.
Is vitamin D deficiency stopping your weight loss?
Low vitamin D is linked to higher body weight and may affect mood and energy, both relevant to weight management. Many UK adults are deficient. If your GP finds low vitamin D, supplementation is recommended (especially October to March). However, vitamin D alone won't cause weight loss; it's a supporting factor alongside diet, activity, and potentially prescription weight loss medication.
Do "weight loss vitamins" sold online actually work?
Most commercial "weight loss vitamin" supplements lack strong scientific evidence. Claims about metabolism-boosting blends, fat-burning capsules, or "detox" vitamins are typically overstated. The most reliable approach to weight management is a reduced-calorie diet, physical activity, and — if eligible — prescription options. Consult your GP before buying expensive supplement packages.
Should you take multivitamins while trying to lose weight?
If you're eating a balanced, reduced-calorie diet, a basic multivitamin can help cover nutritional gaps, though food is the better source. During weight loss, adequate protein, fibre, and micronutrient intake is important to protect muscle and energy. A balanced approach to nutrition supports sustainable weight loss better than calorie restriction alone.
What's the NHS view on vitamins and weight loss?
The NHS does not recommend vitamin supplements as a weight loss strategy. The NHS Weight Loss Plan emphasises diet, activity, and behaviour change. If vitamin deficiencies are present (tested by your GP), supplementation is appropriate. For weight management in the UK, your GP can refer you to specialist tier 3 services where prescription weight loss medication may be considered alongside lifestyle support.
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.