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
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Stomach Injections For Weight Loss in the UK
Stomach injections for weight loss are prescription-only medications that can help eligible UK adults manage their weight more effectively. These once-weekly injectables work by mimicking natural hormones that regulate appetite and fullness. If you're considering weight management through prescription medication, it's important to understand your options, eligibility criteria, and how the NHS and private routes differ. This guide covers the licensed options available to you in the UK and how to explore whether you might be suitable for treatment.
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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.
UK-Licensed Weight Loss Injections Explained
Three prescription weight loss injections are currently licensed in the UK: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). All three are GLP-1 receptor agonists—or in Mounjaro's case, a dual GIP/GLP-1 agonist—meaning they activate hormones that reduce hunger and help you feel fuller after eating.
Mounjaro (once weekly, doses 2.5–15 mg) showed an average weight loss of 15–21% body weight in clinical trials. Wegovy (once weekly, 0.25–2.4 mg) showed approximately 15% average weight loss. Saxenda (daily injection, 0.6–3 mg) is the oldest option and typically produces 5–clinically studied weight loss. All three require a calorie-controlled diet and increased physical activity for best results. Weight loss with any medication varies significantly between individuals, and results are not assured.
Use our free GLP-1 weight loss calculator to estimate potential outcomes at different doses, and check your BMI using our free calculator to understand your starting point.
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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.
Eligibility and How to Access in the UK
To be eligible for prescription weight loss injections in the UK, you typically need a BMI of 30 or above, or BMI of 27–29.9 with at least one weight-related health condition (such as type 2 diabetes, high blood pressure, or cardiovascular disease). People of South Asian, Chinese, Black African, or Black Caribbean heritage may qualify at lower BMI thresholds due to higher health risks at these levels.
NHS access is through specialist tier 3 weight management services—your GP can refer you, though waiting lists vary significantly by region and can be lengthy. Private access is available through GPhC-registered online pharmacies following a clinical assessment with a UK-licensed prescriber. Costs typically range from £129–£320 per month depending on dose. Either route requires a prescription; these are not available over-the-counter.
Start by having a conversation with your GP about your weight management goals. They can assess whether you're eligible, discuss which option might suit you, and either refer you to NHS specialist services or advise on private options. Your GP may also check your blood sugar, blood pressure, and other health markers to ensure a weight loss medication is safe for you. Many GPs are now familiar with these medications and understand both NHS and private pathways, so don't hesitate to ask directly about stomach injections for weight loss if you think you might be eligible.
- 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 do stomach injections for weight loss work?
These injections contain medications (GLP-1 or GIP/GLP-1 agonists) that mimic natural gut hormones. They reduce hunger, increase fullness signals to the brain, and slow how quickly food leaves your stomach. This combination typically leads to eating less and feeling satisfied with smaller portions. Individual response varies.
Are stomach injections available on the NHS in the UK?
Yes, but access is through specialist tier 3 weight management services, not standard GP prescriptions. You'll need a BMI of 30+ or 27+ with weight-related health conditions. Your GP can refer you, though waiting times vary significantly by region. Private access is also available through online prescribers.
What is the difference between Mounjaro and Wegovy?
Both are once-weekly injections. Mounjaro (tirzepatide) is a dual GIP/GLP-1 agonist with average weight loss of 15–21%, while Wegovy (semaglutide) is a GLP-1 agonist with average weight loss around 15%. Mounjaro typically starts at lower doses and titrates up. Individual results vary; neither is assured to work for everyone.
What are the side effects of stomach injections for weight loss?
Common side effects include nausea, diarrhoea, constipation, and stomach discomfort—especially when starting or increasing doses. Most side effects improve over time. Serious side effects are rare but can include pancreatitis. Your prescriber will monitor you and discuss any concerns during your clinical assessment.
Can I get these injections privately without waiting for the NHS?
Yes. GPhC-registered online pharmacies can prescribe these medications following a clinical assessment. You don't need an NHS referral. Costs vary (typically £129–£320/month depending on dose and provider), and you'll need a prescription from a UK-licensed prescriber. It's faster than NHS routes but not covered by health insurance.
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.