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
How To Control Insulin For Weight Loss In The UK
Controlling insulin levels is key to sustainable weight management. Insulin resistance — where your body doesn't respond properly to insulin — makes weight loss harder. The good news? You have options. In the UK, prescription weight loss medications like Mounjaro and Wegovy work by improving how your body handles insulin and regulating appetite. Lifestyle changes also matter, but for eligible adults, medication can provide significant support. This guide covers your UK options and how to find out if you qualify for prescription weight management support.
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 Prescription Options For Insulin Management And Weight Loss
If you're struggling with weight management in the UK, three prescription medications are licensed specifically for this purpose. Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist that helps regulate both appetite and insulin response — clinical trials showed it helped participants lose an average of 15–21% of body weight alongside a reduced-calorie diet. Wegovy (semaglutide) is a GLP-1 receptor agonist with similar effects, supporting an average weight loss of around 15% in trials. Saxenda (liraglutide) is a daily injection option.
All three medications work by helping your body use insulin more effectively and reducing appetite. They're prescription-only and require a clinical assessment to determine suitability. Try our free GLP-1 weight loss calculator above to understand potential outcomes at different doses. Eligibility depends on your BMI and health profile — your GP or a licensed prescriber can assess whether you qualify. Calculate your BMI using our free BMI calculator to check where you stand against NHS thresholds.
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 Versus Private Access And Next Steps
In the UK, you can access prescription weight loss medication through two routes. NHS access is through specialist tier 3/4 weight management services — your GP can refer you, though waiting lists vary significantly by region and can be lengthy. Private access is available through UK-licensed prescribers via online consultations; medication is dispensed by GPhC-registered pharmacies without requiring an NHS referral.
To find out if you're eligible, use our free weight converter and BMI calculator on this page to understand your current weight status. A healthy BMI range is 18.5–24.9 according to NHS guidelines, though for some ethnic groups, lower thresholds apply. Book an appointment with your GP to discuss your options, or contact a private online prescriber for a clinical assessment. Either way, a qualified healthcare professional will evaluate whether prescription medication is appropriate for you and your individual health needs.
- 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.
Does controlling insulin directly cause weight loss?
Controlling insulin improves your body's ability to manage weight, but weight loss also requires a calorie deficit through diet and activity. Insulin-regulating medications help by reducing appetite and cravings, making it easier to maintain a deficit. Individual results vary, and medication works best alongside lifestyle changes.
What's the difference between Mounjaro and Wegovy for insulin control?
Mounjaro is a dual GIP+GLP-1 agonist affecting two insulin-related pathways; Wegovy is a single GLP-1 agonist. Mounjaro showed slightly higher average weight loss in trials (15–21% vs ~15%), but both are effective. Your prescriber will recommend which suits your individual health profile best.
Can I get insulin-controlling weight loss medication on the NHS?
Yes, through specialist weight management services (tier 3/4). Your GP can refer you, but availability and waiting times vary by region. Private prescribing is also available through online consultations if you prefer faster access and don't require NHS referral.
What BMI do I need to qualify for prescription weight loss medication in the UK?
Generally, a BMI of 30 or above, or 27–29.9 with weight-related health conditions (diabetes, high blood pressure, sleep apnoea). For South Asian, Black African, Caribbean, or Chinese adults, lower thresholds may apply. Use our free BMI calculator above to check your starting point.
Are there side effects to insulin-controlling weight loss injections?
Common side effects include nausea, diarrhoea, constipation, and reduced appetite — typically mild and improve over time. Serious side effects are rare but can include pancreatitis symptoms. Your prescriber will discuss all risks during your clinical assessment before issuing a prescription.
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.