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 Vitamin B12 Shots Help With Weight Loss?
Vitamin B12 shots are sometimes marketed for weight loss, but the evidence that B12 alone causes weight loss is limited. B12 is an essential nutrient that supports energy and metabolism, but it is not a weight loss medication. If you're looking for clinically proven weight management options in the UK, prescription weight loss injections like GLP-1 medications (such as Wegovy) have strong trial evidence. Our free GLP-1 weight loss calculator can help you understand what different doses might achieve. Always consult your GP about the best approach for your health.
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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.
What B12 Does (And Doesn't Do) For Weight Loss
Vitamin B12 is essential for energy, red blood cell production, and nerve function. Some clinics claim B12 shots boost metabolism and suppress appetite, but robust clinical trial evidence for weight loss is lacking. B12 may be helpful if you have a genuine B12 deficiency (which can cause fatigue and slow metabolism), but supplementing B12 when your levels are already normal does not typically result in significant weight loss.
B12 and metabolism: B12 helps convert food into energy, so adequate levels support a healthy metabolism. However, extra B12 beyond what your body needs does not accelerate weight loss. Weight loss depends on creating a calorie deficit through diet and physical activity — B12 alone cannot achieve this.
- B12 is water-soluble — excess is excreted in urine, not stored
- If you have low B12, correcting it may improve energy for exercise
- If your B12 is normal, additional shots are unlikely to aid weight loss
- B12 is not a prescription weight loss medication
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.
B12 vs Prescription Weight Loss Injections
If you're seeking prescription weight management options in the UK, medications like Wegovy (semaglutide) and Mounjaro (tirzepatide) have strong clinical trial evidence for weight loss. These are GLP-1 receptor agonist injections approved by the MHRA and prescribed through NHS weight management services or private online assessment. STEP clinical trials showed Wegovy can help participants lose approximately 15% of body weight alongside a reduced-calorie diet.
B12 shots, by contrast, are nutritional supplements without prescription-only status or licence for weight loss. Use our BMI calculator to check your current health metrics, then speak to your GP about whether prescription weight loss medication or other evidence-based approaches are suitable for you. Your GP can assess your individual circumstances and refer you to specialist weight management services if appropriate.
- 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.
Will B12 shots help me lose weight?
B12 shots may help if you have a documented B12 deficiency, as correcting it can improve energy levels. However, if your B12 is already normal, additional B12 is unlikely to cause weight loss. Weight loss requires a calorie deficit. Prescription weight loss injections like Wegovy have clinical trial evidence for weight loss; B12 does not.
Is B12 a prescription weight loss medication?
No. B12 is a vitamin and nutritional supplement, not a prescription weight loss medication. It is not regulated or approved for weight loss by the MHRA. Prescription weight management injections (such as GLP-1 medications) require clinical assessment and a prescription from a licensed healthcare provider.
Can I get B12 shots on the NHS for weight loss?
B12 injections are available on the NHS for people with proven B12 deficiency. They are not prescribed for weight loss specifically. If you're interested in prescription weight management options, ask your GP about referral to a specialist weight management service or discuss NHS weight loss programmes.
What are the alternatives to B12 for weight loss in the UK?
Evidence-based options include: reduced-calorie diet, increased physical activity, NHS weight loss services (Tier 1–3), and prescription medications like Wegovy and Mounjaro (for eligible adults with BMI ≥30 or ≥27 with weight-related health conditions). Your GP can advise which is right for you.
Should I try B12 shots before prescription weight loss medication?
Not necessarily. If you're seeking weight loss, the best approach depends on your individual health, BMI, and preferences. B12 may help if deficient, but it is not a weight loss treatment. Prescription weight loss injections have proven clinical efficacy. Discuss all options with your GP to make an informed decision aligned with your health needs.
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.