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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Weight Loss Jabs in the UK — What You Need to Know
Weight loss injections, commonly called "weight loss jabs" or "slimming jabs", are prescription-only medications licensed in the UK for weight management. These GLP-1 and GIP/GLP-1 receptor agonist injections may help support weight loss alongside dietary changes and increased physical activity. If you're interested in weight management options, understanding what's available on the NHS and privately can help you decide whether to speak with your GP about prescription weight loss medication.
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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 Jabs and How They Work
Three prescription weight loss jabs are currently licensed in the UK:
- Mounjaro (tirzepatide) — a dual GIP and GLP-1 receptor agonist, injected once weekly at doses ranging from 2.5 mg to 15 mg. Clinical trials showed participants lost an average of 15–21% of their body weight.
- Wegovy (semaglutide) — a GLP-1 receptor agonist, injected once weekly at doses up to 2.4 mg. Evidence suggests average weight loss of around 15% of body weight in clinical trials.
- Saxenda (liraglutide) — a GLP-1 receptor agonist, administered as a daily injection at doses up to 3 mg.
All three work by activating hormone pathways that help regulate appetite, reduce food cravings, and promote feeling fuller after meals. Individual results vary significantly, and these medications are most effective when combined with a reduced-calorie diet and physical activity. You can explore potential weight loss outcomes using our GLP-1 weight loss calculator above.
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 Access vs Private Prescription — What's Available to You
On the NHS: Weight loss injections may be prescribed through tier 3 specialist weight management services. Your GP can refer you if you meet eligibility criteria, though NHS availability and waiting times vary significantly across different regions. On the private side: These medications are available through online consultations with UK-licensed prescribers followed by dispensing from registered pharmacies — accessible without NHS referral but at a cost.
To find out which option suits you, speak with your GP about your weight management goals. You can use our free BMI calculator above to check your current BMI, which helps determine eligibility. Your GP will assess your individual circumstances and can guide you towards the right weight management pathway.
On the NHS: Weight loss injections may be prescribed through tier 3 specialist weight management services. Your GP can refer you if you meet eligibility criteria, though NHS availability and waiting times vary significantly across different regions. On the private side: These medications are available through online consultations with UK-licensed prescribers followed by dispensing from registered pharmacies — accessible without NHS referral but at a cost.
To find out which option suits you, speak with your GP about your weight management goals. You can use our free BMI calculator above to check your current BMI, which helps determine eligibility. Your GP will assess your individual circumstances and can guide you towards the right weight management pathway.
- 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.
Who is eligible for weight loss jabs in the UK?
Adults with a BMI of 30 or above, or 27–29.9 with at least one weight-related condition (such as type 2 diabetes, high blood pressure, or sleep apnoea) may be eligible. South Asian, Chinese, Black African, and Black Caribbean adults may qualify at lower BMI thresholds due to higher health risks at lower weights. A GP or prescriber will assess eligibility individually.
How much weight can I expect to lose with weight loss jabs?
Clinical trials show average weight loss of 15–21% of body weight, depending on the medication and dose. However, individual results vary significantly. Weight loss is most effective when combined with a reduced-calorie diet and increased physical activity. Our weight loss calculator can help estimate potential outcomes.
Are weight loss jabs available on the NHS?
Yes, weight loss injections may be prescribed through NHS tier 3 specialist weight management services. Your GP can refer you if eligible, though availability and waiting times vary by region. Private prescriptions are also available through UK-licensed prescribers without NHS referral.
What are the main side effects of weight loss jabs?
Common side effects include nausea, diarrhoea, constipation, and stomach pain, particularly when starting or increasing doses. These often improve over time. Serious side effects are rare but can include severe stomach pain (possible pancreatitis) or gallbladder issues. Always discuss potential side effects with your prescriber.
Do I need to stay on weight loss jabs forever?
Weight loss jabs are typically used for a defined period under medical supervision. Some people continue long-term to maintain weight loss, whilst others use them to establish new eating habits. Your prescriber will discuss the appropriate duration based on your individual response and health goals.
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.