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 Routine For Weight Loss — UK Prescription Options
A structured weight routine for weight loss is most effective when combined with evidence-based support. In the UK, eligible adults can access prescription weight management options alongside diet and exercise, including GLP-1 injections like Mounjaro and Wegovy. These medications work alongside lifestyle changes — not instead of them. Our free GLP-1 weight loss calculator can help you explore potential results, whilst our BMI calculator shows whether you may qualify for prescription support. This guide explains what's available on the NHS and privately, and how to find out if you're eligible.
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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 Prescription Weight Loss Options
Three prescription medications are currently licensed in the UK for weight management and may be considered as part of your weight routine for weight loss:
- Mounjaro (tirzepatide) — a dual GIP and GLP-1 receptor agonist, taken once weekly. Clinical trials showed an average weight loss of 15–21% of body weight over 72 weeks when combined with diet and exercise.
- Wegovy (semaglutide) — a GLP-1 receptor agonist, taken once weekly. Trial data showed an average weight loss of approximately 15% of body weight at 68 weeks alongside lifestyle changes.
- Saxenda (liraglutide) — a GLP-1 receptor agonist, taken as a daily injection. Maximum dose 3 mg per day.
All three are prescription-only medicines requiring clinical assessment. You must have a BMI of 30 or above, or 27 or above with weight-related health conditions (such as type 2 diabetes, high blood pressure, or cardiovascular disease) to be eligible. Individual results vary significantly.
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 — Finding Out If You're Eligible
NHS access: Weight loss medications are available through specialist tier 3 and tier 4 weight management services. You'll need a GP referral and assessment. Availability and waiting times vary significantly by region — some areas have long waiting lists. NICE has approved these medications for NHS use, but access depends on your local integrated care board (ICB).
Private access: You can access prescription weight loss medication through GPhC-registered online prescribing services following a clinical assessment. This doesn't require an NHS referral. If you think you're eligible, start by speaking to your GP, who can assess your health and either refer you to NHS specialist services or discuss private options. Use our BMI calculator to check your starting point, and track your progress with our free progress tracker once you begin treatment.
- 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 BMI do I need to qualify for prescription weight loss medication in the UK?
Adults with a BMI of 30 or above can usually access prescription weight loss treatment. If you have a BMI of 27–29.9 and a weight-related health condition (such as type 2 diabetes, high blood pressure, cardiovascular disease, or sleep apnoea), you may also be eligible. Lower thresholds apply if you're of South Asian, Chinese, Black African, or Black Caribbean heritage — eligibility may start at BMI 27.5 or above. Use our free BMI calculator to find your starting point.
How much weight can I expect to lose with Mounjaro or Wegovy?
Clinical trials showed average weight loss of 15–21% of body weight with Mounjaro and approximately 15% with Wegovy over 68–72 weeks. However, individual results vary significantly. Weight loss depends on your starting weight, genetics, adherence to treatment, diet, and physical activity. These medications are tools to support your routine, not assures. Our GLP-1 weight loss calculator can help you explore potential outcomes.
What's the difference between getting weight loss medication on the NHS versus privately?
NHS access requires a GP referral to specialist weight management services and can involve waiting lists. Private online prescribing services offer faster access without an NHS referral, but you'll pay for the medication. Both routes require a clinical assessment. Speak to your GP first — they can advise on NHS availability in your area or discuss private options if NHS waiting times are long.
Can I use weight loss medication without changing my diet and exercise routine?
No. These medications are most effective alongside a reduced-calorie diet and increased physical activity. They're designed to support your routine, not replace it. Weight loss medications help reduce appetite and support feeling fuller after meals, but the lifestyle changes are essential for sustained results. Your prescriber will provide guidance on diet and activity levels.
Are there side effects I should know about with prescription weight loss injections?
Yes. Very common side effects include nausea, diarrhoea, constipation, and stomach pain, especially when starting or increasing doses. These often reduce over time as your body adjusts. Less common side effects include dizziness, fatigue, and injection site reactions. Serious side effects are rare but can include severe stomach pain (possible pancreatitis) or gallbladder problems. Always discuss potential side effects with your prescriber and report any concerning symptoms.
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.