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
Slimming Injections in the UK — Your Complete Options
Slimming injections are prescription-only weight loss medications now available in the UK for adults with obesity or overweight. Three main options are licensed: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). Each works through different mechanisms, doses, and injection frequencies. Access is available through NHS specialist services or private online prescribing following a clinical assessment. Understanding your options helps you have informed conversations with your GP or prescriber about which might suit your circumstances.
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 Injection Options — How They Compare
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist — the newest option licensed in the UK for weight management. It uses a once-weekly injection with doses ranging from 2.5 mg to 15 mg. Clinical trials showed an average weight loss of approximately 15–21% of body weight, though individual results vary significantly.
Wegovy (semaglutide) is a GLP-1 receptor agonist, also injected once weekly. Doses escalate from 0.25 mg to a maximum of 2.4 mg. STEP clinical trials demonstrated average weight loss of around 15% of body weight alongside reduced-calorie diet and increased physical activity.
Saxenda (liraglutide) is a GLP-1 receptor agonist given as a daily injection (not weekly). Doses range from 0.6 mg to 3 mg daily. It has been available longer than Mounjaro and Wegovy, with established long-term safety data.
All three are prescription-only medicines requiring clinical assessment before prescribing. Results vary between individuals — weight loss depends on genetics, diet adherence, physical activity, and individual metabolism.
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.
Accessing Weight Loss Injections — NHS and Private Routes
NHS access: Weight loss injections are available through NHS specialist tier 3 and tier 4 weight management services. Your GP can refer you if you meet eligibility criteria (typically BMI ≥30, or BMI ≥27 with weight-related health conditions). NHS availability varies significantly by region and local integrated care boards — waiting lists can be several months to over a year in many areas.
Private access: All three medications are available through private online consultations with UK-licensed prescribers. Following a clinical assessment, eligible patients receive a prescription dispensed by a GPhC-registered pharmacy. Private options typically cost £129–£320 per month depending on medication and dose.
Use our free BMI calculator above to check your current BMI and understand eligibility thresholds. Our GLP-1 weight loss calculator can help estimate potential outcomes at different doses if you're considering prescription weight loss support.
- 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's the difference between Mounjaro and Wegovy?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist, while Wegovy (semaglutide) is a GLP-1 agonist only. Clinical trials suggest slightly higher average weight loss with Mounjaro, but both are effective. Mounjaro uses higher doses (up to 15 mg weekly), Wegovy up to 2.4 mg weekly. Individual response varies — your prescriber will help determine which suits you.
Can I get weight loss injections on the NHS?
Yes, weight loss injections are available through NHS specialist weight management services. You'll need a referral from your GP and must meet eligibility criteria (BMI ≥30, or ≥27 with weight-related conditions). NHS availability varies significantly by region — some areas have long waiting lists. Private options are available without NHS referral.
Are prescription slimming injections safe?
All three UK-licensed weight loss injections have undergone rigorous clinical trials and post-market monitoring. Side effects are common but usually mild — nausea, diarrhoea, and constipation are most frequent. Serious side effects are rare. Always discuss safety with your prescriber, especially if you have a history of pancreatitis or gallbladder problems.
How much weight will I lose with slimming injections?
Clinical trials show average weight loss of 14–21% of body weight over 12–18 months, but individual results vary widely. Some people lose significantly more, others less. Weight loss depends on genetics, diet, exercise, medication dose, and how long you take it. Results are not assured, and weight loss requires lifestyle changes alongside medication.
Which slimming injection should I choose?
There's no single "best" option — suitability depends on your personal health circumstances, preference for weekly vs daily injections, and individual response. Your GP or prescriber will assess your eligibility and discuss which medication may be most appropriate. They'll consider your health conditions, other medications, and medical history before recommending a specific option. ```
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.