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
Prozac for Weight Loss — What UK Adults Should Know
Prozac (fluoxetine) is an antidepressant, not a weight loss medication. Although some people experience weight changes while taking it, the UK NHS does not prescribe Prozac specifically for weight management. If you're interested in prescription weight loss medication, the UK has several evidence-based options available through NHS or private channels. This guide explains what's actually available for weight management in the UK 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-Approved Weight Loss Medications — The Actual Options
The UK has three prescription-only medicines licensed specifically for weight management, each with strong clinical evidence behind them:
- Mounjaro (tirzepatide) — A once-weekly injection that activates two hormone pathways. Clinical trials showed average weight loss of 15–21% of body weight over 72 weeks, with participants using the medication alongside reduced-calorie diet and increased physical activity.
- Wegovy (semaglutide) — A once-weekly GLP-1 injection. In clinical trials, adults lost an average of approximately 15% of their body weight on the maximum dose.
- Saxenda (liraglutide) — A once-daily GLP-1 injection, approved for longer and offering similar weight loss outcomes to Wegovy.
All three are prescription-only and require a clinical assessment before being prescribed. Individual results vary significantly, and medication works best alongside lifestyle changes, not instead of them.
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 — How to Access Weight Loss Medication in the UK
NHS access: Weight management medications are prescribed through specialist tier 3 weight management services, not your GP. You'll need a referral, and availability varies significantly by region. Waiting lists can be several months to over a year in many areas.
Private access: Available through GPhC-registered online pharmacies following a clinical consultation. No NHS referral needed, though costs typically range from £129–£320 per month depending on the dose. Try our free GLP-1 weight loss calculator to understand potential outcomes at different doses, and use our BMI calculator to determine your starting position.
- 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.
Why isn't Prozac prescribed for weight loss in the UK?
Prozac is an antidepressant (selective serotonin reuptake inhibitor) licensed to treat depression, anxiety, and OCD. While some people experience weight changes as a side effect, it has no clinical evidence for weight management. The UK approves only Mounjaro, Wegovy, and Saxenda specifically for weight loss, and these are much more effective for this purpose.
Who is eligible for prescription weight loss medication in the UK?
Adults with a BMI of 30 or above, or 27–29.9 with at least one weight-related health condition (diabetes, high blood pressure, heart disease, sleep apnoea). Lower BMI thresholds may apply if you're of South Asian, Chinese, Black African, or Black Caribbean heritage. Use our free BMI calculator to check your current BMI.
How quickly can I get weight loss medication on the NHS?
NHS access is through specialist weight management services, not standard GP prescription. Referral, assessment, and wait times vary by region. Some areas have waiting lists of 6–18 months. Private options are faster — typically available within 1–2 weeks of online consultation.
What should I do if I want to explore weight loss medication?
Start by speaking to your GP about weight management options available in your area. They can discuss NHS services, assess your eligibility, and provide a referral if appropriate. Alternatively, you can access private prescribing through GPhC-registered online services — no referral needed, but you'll pay privately.
Are there other weight loss options besides injections?
Yes. The NHS Weight Loss Plan offers self-help digital tools and community programmes at tier 1. Your GP may refer you to tier 2 community weight management services. Prescription medication is typically tier 3. Bariatric surgery (tier 4) is available for severe obesity with serious health complications.
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.