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
What Vitamins Are Good For Weight Loss?
When you're working towards weight loss in the UK, you might wonder whether vitamins and supplements can help support your goals. The truth is that while certain vitamins play a role in metabolism and energy levels, they're not a substitute for balanced nutrition, physical activity, and calorie deficit. If you're deficient in specific nutrients, supplementation may help — but for sustainable weight management, a food-first approach combined with lifestyle changes is most effective. This guide covers the evidence on vitamins for weight loss, plus how prescription weight loss medication and healthy habits work together.
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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.
Key Vitamins That Support Weight Management
Several vitamins and minerals play a role in metabolism, appetite regulation, and energy production — all important for healthy weight management in the UK:
- B vitamins (B6, B12, folate, niacin) — Support energy metabolism and help convert food into fuel. Deficiency can slow metabolism.
- Vitamin D — Research suggests low vitamin D is linked to higher BMI. Getting adequate sunlight and supplementing in winter months (when UK sun exposure is limited) may help.
- Iron — Essential for oxygen transport and energy. Low iron causes fatigue, reducing your ability to exercise.
- Magnesium — Supports muscle function, energy production, and may help regulate blood sugar.
- Chromium — Some evidence suggests it may reduce sugar cravings and support stable blood glucose.
The key point: these vitamins work best when you're eating a balanced diet. Supplements alone won't create weight loss — you still need a calorie deficit through reduced-calorie diet and increased physical activity. Calculate your personal BMI using our free BMI calculator to understand your current weight status, then work with your GP on a comprehensive plan.
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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 prescription weight loss UK options, it's important to understand that vitamins and medication work differently. Vitamins support general health and fill nutritional gaps — prescription medications like GLP-1 weight loss injections (such as Mounjaro and Wegovy) actively help regulate appetite and food intake. These medications may help you achieve meaningful weight loss when used alongside a reduced-calorie diet and exercise. Our GLP-1 weight loss calculator can help you estimate potential results with prescription medication.
Your GP can assess whether you'd benefit from prescription weight loss treatment based on your BMI, health conditions, and individual circumstances. Vitamins should complement — not replace — these evidence-based approaches. Many people benefit from combining good nutrition (including adequate vitamins), nhs weight loss support, and where appropriate, prescription medication for the best results.
- 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 vitamins alone help me lose weight?
No — vitamins support overall health and metabolism, but weight loss requires a calorie deficit. Vitamins are most effective when combined with a balanced diet, physical activity, and lifestyle changes. If you have a deficiency, supplementing may help improve energy and exercise capacity, indirectly supporting your weight loss efforts.
Should I take vitamin supplements while taking weight loss medication?
This depends on your individual health. Some people taking prescription weight loss injections may benefit from additional B vitamins or vitamin D, especially if they're eating smaller portions. Always inform your prescriber about any supplements you're taking — they can advise whether supplements are appropriate for you.
Is vitamin D important for weight loss?
Research suggests vitamin D deficiency is linked to higher BMI and difficulty losing weight. The UK has limited winter sunlight, so many adults are deficient. Vitamin D supplementation (especially October to March) may support weight management, but it works best alongside a calorie deficit and exercise. Ask your GP about vitamin D testing.
What's the best way to get vitamins for weight loss — food or supplements?
Food first. A balanced diet with plenty of vegetables, whole grains, lean protein, and fruit provides most vitamins you need. Only supplement if you have a documented deficiency or specific dietary restriction. Supplements are useful but cannot replace whole foods. Your GP can test for deficiencies if you're concerned.
Do weight loss injections affect my vitamin absorption?
GLP-1 medications slow gastric emptying, which may slightly affect nutrient absorption. You're also eating smaller portions, so nutrient intake may decrease. Discuss with your prescriber or a dietitian whether you should take B vitamins or other supplements while on prescription weight loss medication. They can personalise advice based on your blood work.
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.