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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Instant Weight Loss Tips: UK Prescription Medication Options
If you're looking for instant weight loss tips that actually work, prescription weight loss medication may be an option worth discussing with your GP. While no weight loss approach is truly "instant", UK-licensed medications like Mounjaro and Wegovy can provide meaningful support for weight management when combined with lifestyle changes. This guide explains the prescription options available, who's eligible, and how to access them through the NHS or privately.
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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: What's Available?
Three prescription medications are currently licensed in the UK specifically for weight management: Mounjaro (tirzepatide), a dual GIP and GLP-1 receptor agonist; Wegovy (semaglutide 2.4 mg), a GLP-1 receptor agonist; and Saxenda (liraglutide), a daily GLP-1 injection. All three work by helping regulate appetite and supporting feelings of fullness.
In clinical trials, Mounjaro helped participants lose an average of 15–21% of their body weight, whilst Wegovy showed average weight loss of approximately 15%. These are prescription-only medicines available only following a clinical assessment by a licensed prescriber. Weight loss with medication requires ongoing commitment to reduced-calorie diet and increased physical activity—medication alone is not a solution.
Eligibility typically includes adults with a BMI of 30 or above, or 27 or above with weight-related health conditions such as type 2 diabetes, high blood pressure, or sleep apnoea. Use our free BMI calculator above to check your personal BMI and understand whether you might fall within typical eligibility ranges for weight loss medication.
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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: How to Find Out If You're Eligible
Access to prescription weight loss medication in the UK varies. NHS access is typically through specialist tier 3 weight management services following a GP referral, though availability and waiting times differ significantly by region. Private access is available through GPhC-registered online prescribing services following an online clinical assessment.
The first step is always a conversation with your GP, who can assess your individual health, discuss whether medication is appropriate, and explain your options. They can refer you to NHS specialist services if eligible, or discuss private options. Your GP will also consider any other health conditions or medications you're taking. Our GLP-1 weight loss calculator can help you explore projected outcomes at different doses, giving you informed questions to ask your prescriber.
NHS approach: Free, but often involves waiting lists. Available in tier 3 specialist services. Requires GP referral and assessment. Regional availability varies widely.
Private approach: Faster access, available without GP referral. Requires online clinical assessment. Costs range approximately £129–£320 monthly depending on dose and provider.
Whichever route you explore, prescription weight loss medication works best alongside behaviour change—diet, physical activity, and monitoring progress. Try our free progress tracker to log your weight management journey and track changes over time. Always inform any prescriber of all medications and health conditions you have.
- 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's the difference between Mounjaro and Wegovy for weight loss?
Mounjaro is a dual GIP and GLP-1 receptor agonist (once-weekly injection, up to 15 mg), whilst Wegovy is a GLP-1-only agonist (once-weekly, up to 2.4 mg). Clinical trials showed Mounjaro slightly higher average weight loss (15–21% vs 15%), but both require prescription, eligibility assessment, and lifestyle changes. Individual results vary significantly.
Am I eligible for prescription weight loss medication on the NHS?
Generally, you may be eligible if you have a BMI of 30 or above, or 27 or above with weight-related health conditions (type 2 diabetes, high blood pressure, sleep apnoea, cardiovascular disease). Lower thresholds apply for South Asian, Chinese, Black African, or Black Caribbean adults. Your GP can assess your individual eligibility and refer you to specialist services if appropriate.
How quickly will I lose weight with prescription medication?
Weight loss typically begins within the first 4 weeks and continues over months. NHS recommends sustainable loss of 0.5–1 kg per week. Clinical trials measured weight loss over 16–72 weeks. Results depend on dose, individual metabolism, adherence to diet and exercise, and other factors. Your prescriber will monitor your progress.
Can I get weight loss injections on the NHS?
Yes, Mounjaro and Wegovy are available on the NHS through specialist tier 3 weight management services. You'll need a GP referral and assessment. Availability and waiting times vary significantly by region and NHS integrated care board. Contact your GP to discuss referral options in your area.
What happens if I stop taking weight loss medication?
Weight regain can occur after stopping medication, particularly if diet and exercise habits haven't been maintained. This is why weight loss medication is typically used alongside permanent lifestyle changes. Your prescriber will discuss the long-term plan and whether ongoing medication, behavioural support, or other strategies suit your situation best.
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.