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
Will B12 Help With Weight Loss?
B12 supplements alone are not an effective weight loss treatment, even though B12 is essential for metabolism and energy. If you're looking for medically-supported weight management in the UK, there are prescription options available. This guide explains what B12 actually does, why prescription weight loss medications work differently, and how to find out if you're eligible for NHS or private treatment.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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-Approved Weight Loss Medications
If you're interested in weight management uk with medical support, the NHS and private prescribers in the UK offer several prescription options. Mounjaro (tirzepatide) and Wegovy (semaglutide) are once-weekly injections licensed for weight management. Saxenda (liraglutide) is a daily injection alternative. These are GLP-1 and GIP receptor agonist medications — they work by regulating appetite, helping you feel fuller after smaller meals, and supporting better food choices.
- Mounjaro: Dual GIP and GLP-1 agonist; average weight loss 15–21% body weight in clinical trials
- Wegovy: GLP-1 agonist; average weight loss around 15% body weight
- Saxenda: GLP-1 agonist; daily injection alternative
These medications are prescription-only and require a clinical assessment. Use our free GLP-1 weight loss calculator 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.
NHS vs Private: How to Get Started
NHS weight loss medication: Available through specialist tier 3 weight management services. You'll need a GP referral. Access varies by region and waiting lists can be lengthy.
Private prescription: Available through GPhC-registered online prescribers. No NHS referral needed. A licensed prescriber will assess your eligibility based on your BMI and health conditions.
Who is eligible? Generally adults with a BMI of 30 or above, or 27–29.9 with weight-related conditions like type 2 diabetes, high blood pressure, or sleep apnoea. Use our BMI calculator to check your starting point, then speak with your GP or a private prescriber about options.
- 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 B12 help you lose weight?
B12 is essential for metabolism and energy production, but B12 supplements alone do not cause weight loss. Some people feel more energised with adequate B12, which may support physical activity, but B12 injections or supplements are not weight loss treatments. If you have a genuine B12 deficiency, your GP should diagnose and treat it.
What do prescription weight loss injections actually do?
Medications like Mounjaro and Wegovy are GLP-1 (and GIP) receptor agonists. They signal to your brain that you're full, reduce cravings, slow stomach emptying, and help regulate appetite hormones. They work alongside a reduced-calorie diet and exercise — they're not replacements for lifestyle changes.
Am I eligible for prescription weight loss medication in the UK?
Generally, yes, if your BMI is 30 or above, or 27–29.9 with weight-related health conditions (type 2 diabetes, high blood pressure, sleep apnoea, heart disease). Your GP or a licensed private prescriber will assess your individual circumstances. Use our BMI calculator to check where you stand.
How much weight can I expect to lose with these medications?
Clinical trials show average weight loss of 15–21% of body weight over several months, but individual results vary significantly. Some people lose more, some less. Weight loss depends on your starting weight, the dose, how consistently you take it, and your lifestyle changes. Results are not assured.
How do I start — NHS or private prescription?
For NHS: ask your GP about referral to a specialist weight management service. For private: consult with a GPhC-registered online prescriber. Both pathways require a clinical assessment. Your GP can also discuss which route suits your situation. Our free progress tracker can help you monitor progress once you've started treatment.
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.