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
Does B12 Aid In Weight Loss?
B12 is an essential vitamin that plays a crucial role in energy production and metabolism, but evidence shows it does not directly aid weight loss in people with normal B12 levels. However, if you have a B12 deficiency, correcting it may support better energy and metabolism. For actual weight management in the UK, prescription medications like Mounjaro and Wegovy have strong clinical evidence. If you're considering weight loss options, your GP can assess whether you're eligible for prescription treatment alongside lifestyle changes.
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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.
UK-Licensed Prescription Weight Loss Options
If you're interested in weight management in the UK, several prescription medications have proven clinical effectiveness. Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist that clinical trials showed may help adults lose an average of 15–21% of body weight. Wegovy (semaglutide) is a GLP-1 injection licensed for weight loss, with trials showing approximately 15% average weight loss. Saxenda (liraglutide) is a daily GLP-1 injection also available in the UK.
These prescription weight loss medications are only available for adults with a BMI of 30 or above, or 27–29.9 with weight-related health conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease. Individual results vary significantly, and these medications work alongside reduced-calorie diet and increased physical activity. Use our free GLP-1 weight loss calculator above to explore potential outcomes 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.
Getting Prescription Weight Loss Support in the UK
Access to prescription weight loss medication in the UK comes through two main routes. The NHS route involves referral from your GP to a specialist tier 3 weight management service. However, NHS availability varies significantly by region, and waiting lists can be lengthy in many areas. The private route offers faster access through an online consultation with a UK-licensed prescriber, followed by dispensing from a GPhC-registered pharmacy.
Your GP is the best starting point—they can assess your eligibility, discuss your health conditions, and advise on the most suitable pathway. Even if prescription medication isn't appropriate for you, your GP can recommend evidence-based weight management support. Check your BMI using our free BMI calculator above to understand where you stand according to NHS guidelines.
- 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.
Does vitamin B12 directly cause weight loss?
No. B12 is essential for energy and metabolism, but evidence shows it does not directly cause weight loss in people with adequate B12 levels. If you have a B12 deficiency, correcting it may improve energy and support better physical activity, but this is different from B12 promoting weight loss itself.
What prescription weight loss medications are available in the UK?
Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide) are UK-licensed for weight management. All three are GLP-1 or dual GIP/GLP-1 receptor agonists. Clinical trials show average weight loss of 15–21% alongside reduced-calorie diet and increased activity. Individual results vary considerably.
Who is eligible for prescription weight loss medication in the UK?
Adults with a BMI of 30 kg/m² or above, or 27–29.9 with weight-related health conditions (type 2 diabetes, hypertension, cardiovascular disease) may be eligible. Lower BMI thresholds apply for South Asian, Chinese, Black African, and Black Caribbean adults. Your GP or prescriber will assess your individual suitability.
Is prescription weight loss medication available on the NHS?
Yes, through specialist tier 3 weight management services. However, NHS availability and waiting times vary significantly by region. Private access is also available through online consultations with UK-licensed prescribers. Your GP can advise on your local NHS options and eligibility.
Should I take B12 supplements for weight loss?
Not specifically for weight loss. If you have a diagnosed B12 deficiency, your GP may prescribe B12 treatment, which can improve energy and support overall health. For weight loss, evidence-based options include lifestyle changes and, if eligible, prescription medications. Always consult your GP before starting supplements.
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.