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 at Pharmacies — Your NHS & Private Options
Weight loss jabs, commonly called slimming injections or fat jabs, are prescription medications available through both NHS specialist services and private UK pharmacies. These GLP-1 and dual-action receptor agonist injections help manage weight management uk alongside diet and exercise. Access depends on your BMI, health conditions, and whether you meet NHS weight loss eligibility criteria. This guide explains what these injections are, who can access them, and how to find out if you're eligible for prescription weight loss treatment in the UK.
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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 Injection Options
Three prescription weight loss medications are currently licensed in the UK:
- 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 an average weight loss of 15–21% of body weight over 72 weeks, alongside reduced-calorie diet and increased physical activity. Individual results vary significantly.
- Wegovy (semaglutide) — A GLP-1 receptor agonist. Once-weekly injection up to 2.4 mg. STEP trials demonstrated approximately 15% average body weight loss at the maximum dose.
- Saxenda (liraglutide) — A GLP-1 receptor agonist. Daily injection up to 3 mg. The older of the three options, with evidence supporting modest weight loss for eligible adults.
All three are prescription-only medicines requiring clinical assessment before dispensing. They work by affecting hormones that regulate appetite and blood sugar, supporting feelings of fullness and reducing food cravings. Results depend on individual factors, adherence, and lifestyle changes.
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 Started
NHS access: Weight loss injections are available through specialist tier 3 and tier 4 weight management services. You'll need a GP referral and assessment showing BMI of 30 kg/m² or above, or 27–29.9 kg/m² with weight-related health conditions (type 2 diabetes, high blood pressure, cardiovascular disease, sleep apnoea). Waiting lists vary by region — some areas have significant delays.
Private access: Available through registered online pharmacies following an online clinical assessment with a UK-licensed prescriber. No NHS referral needed. Use our GLP-1 weight loss calculator to estimate potential results at different doses, and our BMI calculator to check your eligibility status. Your GP can also discuss whether prescription weight loss medication is right for you.
- 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.
What are weight loss jabs and how do they work?
Weight loss jabs contain GLP-1 receptor agonist medications (or dual GIP/GLP-1 agonists like Mounjaro) that mimic natural hormones. They reduce appetite, increase feelings of fullness, and slow stomach emptying. All are prescription-only, once-weekly injections used alongside diet and exercise for weight management.
Who is eligible for prescription weight loss medication on the NHS?
NHS eligibility typically requires BMI ≥30 kg/m² or BMI 27–29.9 with weight-related health conditions (type 2 diabetes, hypertension, cardiovascular disease, sleep apnoea). South Asian, Black African, or Chinese adults may have lower thresholds. You'll need a GP referral to specialist weight management services.
Can I get weight loss injections privately if I don't qualify for the NHS?
Yes. Private UK pharmacies dispense these medications following online clinical assessment with a UK-licensed prescriber. No NHS referral is required. Costs vary by dose and provider, typically ranging from £129–£320 monthly. Eligibility criteria may differ from NHS thresholds.
What results can I expect from weight loss jabs?
Clinical trials showed average weight loss of 15–21% body weight with Mounjaro and approximately 15% with Wegovy over several months. Individual results vary significantly based on adherence, diet, exercise, and personal factors. Results are not assured — always discuss realistic expectations with your prescriber.
Are there side effects with weight loss injections?
Common side effects include nausea, diarrhoea, vomiting, and constipation, typically most noticeable at the start or after dose increases. Most ease over time. Serious side effects are rare but include severe stomach pain (possible pancreatitis) and allergic reactions. Always report unexpected symptoms to your prescriber or GP.
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.