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
Weight Reducing Injections in the UK
Weight reducing injections are prescription-only medicines that can support weight management in UK adults who meet specific health criteria. These injectable medications work by helping regulate appetite and support feeling fuller after meals. Access in the UK is through NHS specialist services or private clinical assessment, and they're always used alongside healthy weight management practices. Understanding how they work, who qualifies, and what to expect is essential before discussing them with your GP.
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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 Reducing Injections Work in the UK
Weight reducing injections licensed in the UK are GLP-1 receptor agonists or dual GIP/GLP-1 agonists — medications that mimic natural gut hormones. These include tirzepatide (Mounjaro) and semaglutide (Wegovy), both approved by the MHRA for weight management in UK adults.
These medications work by:
- Signalling to your brain that you feel full sooner
- Reducing food cravings and appetite
- Slowing how quickly food leaves your stomach
- Supporting better blood sugar control
In clinical trials, people using these injections alongside reduced-calorie diets and increased physical activity lost an average of 15–21% of their body weight, though individual results vary significantly. They are prescription-only medicines requiring clinical assessment before being prescribed. Weight loss is not assured, and results depend on lifestyle changes, individual metabolism, and adherence to the medication schedule.
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.
UK Eligibility and NHS Access
In the UK, weight reducing injections may be prescribed to adults with a BMI of 30 or above, or 27–29.9 with weight-related health conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease. For people of South Asian, Chinese, Black African, or Black Caribbean backgrounds, lower BMI thresholds apply due to higher health risks at lower weights.
NHS access: Available through tier 3 specialist weight management services — referral from your GP is typically required, though waiting lists vary significantly by region. Private access: Available through GPhC-registered online pharmacies following a clinical assessment. Use our free BMI calculator to check your starting point, and discuss eligibility with your GP or a licensed prescriber to explore whether this treatment is suitable for your health situation.
Before starting weight reducing injections, your prescriber will assess your medical history, current medications, and lifestyle to ensure safety. Side effects are common but usually temporary — nausea, diarrhoea, and constipation are most frequent. Important: These medications require proper storage (refrigeration for unopened pens), weekly injections, and ongoing monitoring by your healthcare provider.
Track your progress using our progress tracker if you start treatment, and maintain regular contact with your prescriber. Use our weight converter to track changes between kg, stone, and pounds. Always follow your prescriber's guidance on dosing, storage, and when to seek urgent medical attention — particularly for severe stomach pain or allergic reactions.
- 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.
Are weight reducing injections available on the NHS in the UK?
Yes, tirzepatide (Mounjaro) and semaglutide (Wegovy) are available through NHS specialist tier 3 weight management services. However, access varies significantly by region, waiting lists can be lengthy, and referral from your GP is usually required. Availability depends on your local Integrated Care Board (ICB) commissioning decisions.
How much weight can I expect to lose with weight reducing injections?
Clinical trials show average weight loss of 15–21% of body weight at the highest doses over 68–72 weeks, alongside a reduced-calorie diet and physical activity. However, individual results vary significantly — some people lose more, others less. Weight loss is not assured, and results depend on adherence, lifestyle, and individual metabolism.
What are the main side effects of weight reducing injections?
The most common side effects are nausea, diarrhoea, vomiting, and constipation — usually temporary and mild. Less common are headache, fatigue, and injection site reactions. Serious side effects like severe stomach pain or allergic reactions are rare but require urgent medical attention. Your prescriber will discuss individual risk factors with you.
Can I get weight reducing injections privately in the UK?
Yes, weight reducing injections are available through private online prescribing services in the UK. You'll need a consultation with a UK-licensed prescriber, who will assess your eligibility. If approved, your prescription is dispensed by a GPhC-registered pharmacy. Costs vary by dose and provider, typically ranging from £129–£320 per month.
Do I need to change my diet and exercise if I take weight reducing injections?
Yes — weight reducing injections are always used alongside a reduced-calorie diet and increased physical activity. They support weight loss by helping you eat less and feel fuller sooner, but they are not replacements for healthy lifestyle changes. NHS guidance emphasises that sustained weight loss requires both medication and behaviour change.
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.