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
What Are the Cheapest Weight Loss Injections in the UK?
Weight loss injections are prescription-only medications available in the UK for eligible adults. The main options are Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). Cost varies depending on dose, supplier, and whether you access treatment through the NHS or privately. This guide explains what's available, how to find out if you're eligible, and how much you can expect to pay. Use our free GLP-1 weight loss calculator to explore potential outcomes with medication, alongside our BMI calculator to check your current health status.
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 Injections and Their Costs
Three prescription weight management injections are currently licensed in the UK:
- Mounjaro (tirzepatide) — dual GIP and GLP-1 receptor agonist, once-weekly injection. Doses range from 2.5 mg to 15 mg. Private cost: approximately £129–£320 per month depending on dose.
- Wegovy (semaglutide) — GLP-1 receptor agonist, once-weekly injection. Doses range from 0.25 mg to 2.4 mg. Private cost: approximately £150–£280 per month depending on dose.
- Saxenda (liraglutide) — GLP-1 receptor agonist, daily injection. Doses range from 0.6 mg to 3 mg. Private cost: approximately £180–£280 per month.
Clinical trials showed these medications can help participants lose an average of 15–21% of body weight alongside a reduced-calorie diet and increased physical activity. Individual results vary significantly. All three are prescription-only and require a clinical assessment before being prescribed.
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 and Finding the Cheapest Option
If you access weight loss injections through the NHS, there is no prescription cost (you only pay standard prescription fees of £9.90 per item in England). However, NHS availability is limited. You'll need a GP referral to a tier 3 specialist weight management service, and waiting lists can be several months long in many areas. Regional variation is significant—some ICBs offer these medications, others do not.
Privately, cost depends on the specific medication, dose, and provider. Starting doses are generally cheaper than maximum doses. Compare prices across GPhC-registered online prescribing services, but always check that the prescriber is UK-licensed and the pharmacy is registered. The cheapest option may not be the best option—ensure you're assessed properly by a qualified prescriber.
To find out if you're eligible, check if your BMI is 30 or above, or 27–29.9 with a weight-related health condition (type 2 diabetes, high blood pressure, sleep apnoea, cardiovascular disease, or abnormal blood fats). Use our free BMI calculator to check your current BMI and healthy weight range for your height. If you're eligible, speak to your GP about NHS options first—referral is free. If NHS waiting lists are too long or you don't meet local criteria, private prescription may be your option. Always compare cost per dose rather than cost per month, as different starting protocols affect total monthly cost.
- 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.
Is there a cheaper alternative to Mounjaro and Wegovy?
Saxenda (liraglutide) is sometimes cheaper, but it's a daily injection whereas Mounjaro and Wegovy are once-weekly. Costs vary across providers. Starting doses of any medication are cheaper than maximum doses. Compare prices across GPhC-registered UK pharmacies, but prioritise proper clinical assessment over lowest cost.
Can I get weight loss injections free on the NHS?
Yes, if prescribed through an NHS specialist weight management service (tier 3). GP referral is required and availability varies by region. There is no prescription fee beyond the standard £9.90 charge in England. Private access is available without NHS referral but involves a fee.
What if my BMI is 27 and I don't have health conditions—am I eligible?
Generally no, unless you have a weight-related health condition like type 2 diabetes, high blood pressure, sleep apnoea, or cardiovascular disease. Your GP or a private prescriber can assess your individual circumstances. Use our BMI calculator to check your current status and discuss options with your GP.
How much weight loss can I expect, and is it worth the cost?
Clinical trials show participants lost an average of 15–21% of body weight over 68–72 weeks alongside diet and exercise changes. Individual results vary. Even a 5–clinically studied weight loss can reduce health risks. Costs vary from £129–£320 monthly. A GP or prescriber can help you assess whether medication is suitable for you based on your health.
Are Mounjaro and Wegovy the same thing?
No. Both are once-weekly injections for weight management, but they work differently. Mounjaro is a dual GIP+GLP-1 agonist (trials showed ~21% average weight loss), while Wegovy is a GLP-1 agonist alone (trials showed ~15% average weight loss). Costs are similar. Your prescriber will help choose what's appropriate for you.
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.