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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One Month Swimming Weight Loss with UK Medication Support
Swimming is an excellent low-impact exercise that burns calories and builds fitness, but sustainable weight loss typically requires more than exercise alone. For adults in the UK with a BMI of 30 or above, or 27 or above with weight-related health conditions, prescription weight management options are available. Combined with regular swimming and dietary changes, medications like Mounjaro and Wegovy may help support your weight loss journey. Your GP can advise whether prescription weight loss medication is suitable for you.
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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: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). These are available through NHS specialist weight management services or private prescribing following clinical assessment.
Mounjaro is a once-weekly GLP-1 and GIP receptor agonist. Clinical trials showed participants lost an average of 15–21% of their body weight over 72 weeks alongside reduced-calorie diet and exercise.
Wegovy is a once-weekly GLP-1 receptor agonist. In STEP trials, participants achieved an average weight loss of approximately 15% of body weight at the highest dose.
Saxenda is a daily GLP-1 injection, with evidence supporting average weight loss of around 5–10% of body weight.
All three require a prescription and clinical assessment before starting. Our free GLP-1 weight loss calculator can help you explore potential weight loss projections at different doses.
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 Prescription
NHS access: Referral to a tier 3 specialist weight management service through your GP. Availability varies significantly by region, and waiting lists can be lengthy. Once assessed, medications may be prescribed within the NHS specialist service.
Private access: Available through GPhC-registered online prescribing services following a consultation with a UK-licensed prescriber. Access does not require NHS referral. Costs range from approximately £129–£320 per month depending on medication and dose.
Whichever route you choose, prescription weight loss medication works best alongside lifestyle changes: regular physical activity like swimming, a calorie-controlled diet, and behaviour change support. Speak with your GP about which option is most appropriate for your circumstances.
- 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.
Can swimming alone help me lose weight in one month?
Swimming burns significant calories and is excellent for fitness and overall health. However, meaningful weight loss typically requires a calorie deficit, which usually means combining exercise with dietary changes. The NHS recommends losing 0.5–1 kg per week for sustainable results. One month of swimming alongside a reduced-calorie diet may result in 2–4 kg loss, depending on frequency and intensity.
Who is eligible for prescription weight loss medication in the UK?
Adults with a BMI of 30 or above, or 27 or above with weight-related health conditions (such as high blood pressure, type 2 diabetes, or sleep apnoea), may be eligible. South Asian, Chinese, Black African, and Black Caribbean adults may qualify at slightly lower BMI thresholds. Your GP can assess whether you meet criteria for prescription treatment.
Can I use prescription weight loss medication alongside exercise like swimming?
Yes. Prescription medications work best when combined with regular physical activity and dietary changes. Swimming is an ideal low-impact exercise to pair with medication because it builds fitness without excessive joint stress. Always inform your prescriber about your exercise routine and any lifestyle changes you're making.
How quickly do Mounjaro or Wegovy work?
Both medications are titrated over several weeks to reach therapeutic doses. Most users begin to notice appetite reduction within the first few weeks, but significant weight loss typically becomes apparent after 8–12 weeks of treatment. Results vary between individuals. The medications are meant for long-term use alongside lifestyle changes, not short-term quick fixes.
What should I do first if I want to explore prescription weight loss options?
Start by booking an appointment with your GP to discuss your weight and health. Use our free BMI calculator to calculate your current BMI and check your eligibility category. Your GP can refer you to specialist services via the NHS, or discuss private prescribing options. A full health assessment is required before any prescription medication can be started.
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.