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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How to Buy Weight Loss Injections in the UK
Weight loss injections are available in the UK through both NHS specialist services and private prescribing, but they are prescription-only medicines that require a clinical assessment. The most commonly prescribed options are Wegovy (semaglutide) and Mounjaro (tirzepatide), both of which may help support weight management alongside diet and exercise. This guide explains UK eligibility, how to access weight loss medication through prescription weight loss routes, costs, and what to expect. Individual results vary, and you'll need a clinical assessment from a UK-licensed prescriber before being prescribed any weight loss injection.
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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.
How Weight Loss Injections Work and UK Eligibility
Wegovy (semaglutide) and Mounjaro (tirzepatide) are GLP-1 receptor agonist medications that work by helping regulate appetite and supporting a feeling of fullness after smaller meals. In clinical trials, Wegovy helped participants lose an average of around 15% of body weight, while Mounjaro showed average losses of 15–21%, though individual results vary significantly. Both are prescription-only medicines available only following a clinical assessment.
In the UK, you may be eligible for weight loss injection if you have:
- A BMI of 30 kg/m² or above, or
- A BMI of 27–29.9 kg/m² with at least one weight-related health condition (type 2 diabetes, high blood pressure, sleep apnoea, or cardiovascular disease)
- For South Asian, Chinese, Black African, or Black Caribbean adults, lower BMI thresholds may apply (from BMI 27.5)
You must also be aged 18 or over, not pregnant, and able to commit to lifestyle changes including diet and physical activity alongside medication.
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 Prescribing in the UK
NHS Route: Weight loss injections are available through specialist tier 3 and tier 4 weight management services, accessed by referral from your GP. NICE has approved tirzepatide (Mounjaro) for use in these services. However, NHS access varies significantly by region and ICB (integrated care board), and waiting lists can be several months or longer. Availability depends on local commissioning decisions.
Private Route: Private prescribing through GPhC-registered online pharmacies is available without NHS referral. You'll have an online consultation with a UK-licensed prescriber, and if approved, receive a prescription and medication dispensed by a registered pharmacy. This typically costs between £129–£320 per month depending on dose and provider. You can use our free GLP-1 weight loss calculator to estimate potential results at different doses before starting.
- 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 Wegovy and Mounjaro?
Both are prescription-only weight loss injections available in the UK, but they work differently. Wegovy (semaglutide) is a GLP-1 receptor agonist, while Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist. In clinical trials, Mounjaro showed slightly higher average weight loss (15–21%) compared to Wegovy (around 15%), but individual results vary. Both require clinical assessment and regular prescriber monitoring.
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 to a tier 3 or 4 weight management service. However, availability varies significantly by region, and waiting times can be lengthy. Private prescribing without NHS referral is also available through registered online clinics, though this involves a cost.
Am I eligible for a weight loss injection?
You may be eligible if you have a BMI of 30 or above, or 27–29.9 with weight-related health conditions (diabetes, high blood pressure, sleep apnoea, or heart disease). You must be at least 18, not pregnant, and committed to lifestyle changes. For South Asian, Chinese, or Black African heritage, lower thresholds apply. A prescriber will assess your individual eligibility.
How much do weight loss injections cost privately?
Private weight loss injections typically cost £129–£320 per month depending on the medication, dose, and provider. Costs increase as you escalate to higher doses. Costs are higher upfront than NHS, but you avoid waiting lists. Some private providers offer payment plans or package deals.
How quickly will I lose weight on a weight loss injection?
Clinical trials showed average weight loss of around 0.5–1 kg per week alongside diet and exercise, though results vary significantly. Some people lose more, some less. Weight loss typically continues for the first 12–16 weeks on maximum dose, then plateaus. Use our free BMI calculator and weight loss calculator to track your personal baseline and set realistic 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.