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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What's the Best Weight Loss Injection for Home Use in the UK?
There are three prescription weight management injections available in the UK that you can use at home: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). All three are NHS-recognised options, though availability varies. The "best" injection depends on your individual health, medical history, and eligibility. Both Mounjaro and Wegovy are once-weekly injections, whilst Saxenda is a daily injection. This guide covers what each option is, who's eligible, and how to access prescription weight loss medication in the UK through both NHS and private routes.
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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 Weight Loss Injections: Your Home Options
Three prescription injections are licensed in the UK for weight management and can be self-administered at home:
- Mounjaro (tirzepatide) — A dual GIP and GLP-1 receptor agonist. Once-weekly injection (2.5 mg to 15 mg). Clinical trials showed an average weight loss of 15–21% of body weight over 72 weeks when combined with a reduced-calorie diet and physical activity.
- Wegovy (semaglutide) — A GLP-1 receptor agonist. Once-weekly injection (0.25 mg to 2.4 mg). Evidence from clinical trials suggests average weight loss of around 15% of body weight at the maximum dose.
- Saxenda (liraglutide) — A GLP-1 receptor agonist. Daily injection (0.6 mg to 3 mg). Approved for weight management in eligible adults, though less commonly prescribed in the UK than the once-weekly options.
All three work by mimicking natural hormones that help regulate appetite and support feeling fuller after eating. Individual results vary significantly, and all are most effective when combined with lifestyle changes. Try our GLP-1 weight loss calculator to estimate potential weight loss 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 Access: How to Get Weight Loss Injections
NHS access: Weight loss injections are available through NHS specialist tier 3 and tier 4 weight management services, but you'll need a GP referral. Availability and waiting times vary dramatically by region — some areas have long waiting lists. Your GP can assess your eligibility based on your BMI and health conditions.
Private access: You can access all three injections privately through GPhC-registered online prescribing services. A UK-licensed prescriber will conduct an online clinical assessment to confirm eligibility. Private costs range from approximately £129–£320 per month depending on dose and provider. To find out if you're eligible, calculate your BMI using our free BMI calculator — you'll typically need a BMI of 30 or above, or 27+ with weight-related health conditions. Start by speaking with your GP about options, or pursue a private clinical assessment.
- 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.
Can I inject weight loss medication at home myself?
Yes. Mounjaro, Wegovy, and Saxenda are all designed for self-injection at home. They come as pre-filled pens or devices with clear instructions. Most people inject into the stomach, thigh, or upper arm. Your prescriber or pharmacist will show you how to inject safely and correctly before you start.
Which weight loss injection is most effective?
Clinical trials suggest Mounjaro may produce slightly higher average weight loss (15–21%) compared to Wegovy (approximately 15%), but individual results vary considerably. The "best" option depends on your health profile, any other medications you take, and what your prescriber recommends following a clinical assessment. Effectiveness also depends on diet and physical activity.
What are the main side effects of weight loss injections?
The most common side effects are nausea, diarrhoea, constipation, and stomach pain. These typically improve over time as your body adjusts. Serious side effects are rare but can include pancreatitis (severe stomach pain) and gallbladder problems. Always report unexpected symptoms to your prescriber or GP immediately.
How much weight will I lose with a weight loss injection?
Average weight loss varies — clinical trials showed 15–21% for Mounjaro and around 15% for Wegovy when combined with a reduced-calorie diet and exercise. However, individual results differ significantly based on your starting weight, adherence to lifestyle changes, dose, and personal metabolism. Our GLP-1 weight loss calculator can provide a personalised estimate.
How do I know if I'm eligible for weight loss injections in the UK?
You're typically eligible if you have a BMI of 30 or above, or a BMI of 27–29.9 with weight-related health conditions (diabetes, high blood pressure, sleep apnoea, heart disease). South Asian, Chinese, Black African, and Black Caribbean adults may be eligible at lower BMI thresholds. Your GP or a private prescriber will assess your individual eligibility during a clinical consultation.
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.