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
Fish Is Good for Weight Loss — But What About Prescription Help?
Fish is genuinely beneficial for weight management — it's high in protein, low in saturated fat, and supports satiety. However, if you're struggling with weight despite eating well, prescription weight loss medication may be an option. The UK has three licensed medications: Mounjaro, Wegovy, and Saxenda. These are available through NHS weight management services or private prescribing for eligible adults. This guide explains what's available, how to access it, and whether you might qualify for prescription support alongside healthier eating choices like increasing fish intake.
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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.
UK-Licensed Weight Loss Medications
Three prescription-only weight loss injections are licensed in the UK:
- Mounjaro (tirzepatide) — a once-weekly dual GIP and GLP-1 receptor agonist. Clinical trials showed average weight loss of 15–21% of body weight at the maximum 15mg dose over 72 weeks, alongside dietary changes and physical activity.
- Wegovy (semaglutide) — a once-weekly GLP-1 receptor agonist. Clinical trials demonstrated approximately 15% average weight loss at the maximum 2.4mg dose over 68 weeks with lifestyle support.
- Saxenda (liraglutide) — a once-daily GLP-1 injection, the longest-established option in the UK. Average weight loss is typically 5–10% of body weight.
All three work alongside reduced-calorie eating and increased physical activity — not instead of lifestyle changes. Individual results vary significantly based on adherence, diet, and exercise.
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.
Who Can Access Weight Loss Medication in the UK?
Eligibility for prescription weight loss medication in the UK depends on BMI and health status. Adults with a BMI of 30 or above, or a BMI of 27–29.9 with at least one weight-related health condition (such as type 2 diabetes, high blood pressure, or sleep apnoea), may qualify. For South Asian, Chinese, Black African, or Black Caribbean adults, lower BMI thresholds apply due to higher cardiovascular risk. Use our free BMI calculator above to check your current BMI. Eligibility is assessed individually — your GP can discuss whether NHS specialist weight management services are available in your area, or you can access private prescribing through a UK-licensed online prescriber following a clinical assessment.
- 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 eating more fish help with weight loss?
Yes. Fish is high in protein (which supports satiety), low in saturated fat, and nutrient-dense. Fatty fish like salmon and mackerel contain omega-3 fatty acids linked to cardiovascular health. Including fish regularly as part of a reduced-calorie diet and nhs weight loss strategy supports sustainable weight management. However, total calorie intake still matters most.
What's the difference between Mounjaro and Wegovy for weight loss?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist showing average weight loss of 15–21% in trials. Wegovy (semaglutide) is a single GLP-1 agonist with average weight loss around 15%. Both are once-weekly injections. Mounjaro may be more potent, but individual results vary. Your prescriber will assess which is more suitable based on your health profile.
Can I get weight loss injections on the NHS?
Yes, but access is through specialist tier 3 weight management services. Your GP can refer you, though waiting lists vary significantly by region. Private prescribing is also available without an NHS referral. Both routes require a clinical assessment confirming you meet eligibility criteria and that prescription weight loss medication is appropriate for you.
How quickly can I expect weight loss with prescription medication?
Weight loss typically becomes noticeable after 4–8 weeks, with continued progress over months. Clinical trials show meaningful results over 12–24 weeks. However, glp-1 weight loss is not assured — it works best alongside reduced-calorie eating and increased physical activity. Track your progress using our free progress tracker to monitor changes in weight and how you feel.
Are weight loss injections safe to use long-term?
All three UK-licensed medications have undergone clinical trials and are monitored by the MHRA. Common side effects include nausea and digestive changes (usually mild and temporary). Serious side effects are rare but can include pancreatitis or gallbladder problems. Your prescriber will monitor you regularly. Discuss any concerns with your GP or prescriber — long-term safety data continues to grow.
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.