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
New Injection For Weight Loss — UK Options
If you're looking for a new injection for weight loss available in the UK, there are several prescription-only options now licensed for weight management. These GLP-1 and dual-action medications may help support weight loss when combined with lifestyle changes. This guide explains what's available, how they work, and whether you might be eligible through the NHS or privately. Always consult your GP before considering any weight loss medication.
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-Licensed Weight Loss Injections
Three prescription weight management injections are currently licensed in the UK for eligible adults:
- Mounjaro (tirzepatide) — A dual GIP and GLP-1 receptor agonist. Once-weekly injection with doses ranging from 2.5 mg to 15 mg. Clinical trials showed participants lost an average of 15–21% of their body weight over 72 weeks alongside dietary changes and increased physical activity.
- Wegovy (semaglutide) — A GLP-1 receptor agonist. Once-weekly injection, maximum dose 2.4 mg. Clinical trial data showed average weight loss of approximately 15% of body weight at the highest dose.
- Saxenda (liraglutide) — A GLP-1 receptor agonist. Daily injection, maximum dose 3 mg. The longer-established option in the UK for weight management.
All three work by activating hormone pathways that may help regulate appetite, reduce food cravings, and support feeling fuller after meals. Individual results vary significantly based on lifestyle factors, genetics, and adherence to treatment.
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 Access and Eligibility
NHS access: Weight loss injections are available through specialist tier 3 weight management services following GP referral. Eligibility typically requires 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. Lower thresholds apply for adults of South Asian, Chinese, Black African, or Black Caribbean heritage. Waiting lists for NHS services vary significantly by region.
Private access: Available through GPhC-registered online pharmacies following a clinical assessment with a UK-licensed prescriber. No NHS referral needed, though costs vary by dose and provider. Before starting any prescription weight loss medication, use our free BMI calculator to understand your current BMI category and eligibility framework. Your GP can provide personalised guidance about whether medication suits your individual health needs and circumstances.
- 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.
How does a new weight loss injection work?
These injections are GLP-1 receptor agonists (or dual GIP/GLP-1 agonists in the case of Mounjaro). They activate natural hormone pathways that signal fullness to your brain, reduce appetite and cravings, slow how quickly food leaves your stomach, and may support healthy fat utilisation. They are not insulin and do not work like insulin.
Am I eligible for a weight loss injection on the NHS?
You may be eligible if you have a BMI of 30 or above, or 27–29.9 with at least one weight-related health condition (type 2 diabetes, high blood pressure, heart disease, or sleep apnoea). Lower BMI thresholds apply if you're of South Asian, Chinese, Black African, or Black Caribbean heritage. Ask your GP about referral to specialist weight management services in your area.
What's the difference between Mounjaro and Wegovy?
Mounjaro is a dual GIP and GLP-1 agonist; Wegovy is GLP-1 only. Mounjaro doses range to 15 mg weekly; Wegovy maxes at 2.4 mg weekly. Clinical trial averages suggest Mounjaro may produce slightly higher weight loss, though individual results vary. Both are once-weekly injections. Your prescriber will recommend the most suitable option for you.
What are the common side effects of weight loss injections?
Very common side effects include nausea, diarrhoea, vomiting, and constipation, typically most noticeable when starting or increasing doses. Many side effects diminish over time. Less common are indigestion, fatigue, dizziness, and injection site reactions. Serious side effects are rare but can include severe stomach pain (possible pancreatitis). Always report persistent or concerning symptoms to your prescriber.
Do I need to change my diet and exercise when taking a weight loss injection?
Yes. These injections work best alongside a reduced-calorie diet and increased physical activity. They are not a substitute for lifestyle changes — they support and enhance them. The NHS recommends sustainable weight loss of 0.5–1 kg per week. Track your progress using our free progress tracker and discuss dietary and exercise changes with your GP or a registered dietitian.
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.