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
Fluoxetine and Weight Loss: What You Need to Know
Fluoxetine is an SSRI antidepressant prescribed in the UK to treat depression, anxiety, and OCD. While some people experience weight changes when taking fluoxetine, it's not a weight loss medication. If you're interested in prescription weight loss medication in the UK, licensed options like Mounjaro and Wegovy are specifically designed for weight management and work differently. This guide explains how fluoxetine affects weight and what weight management UK options are actually available through the NHS and private prescribing.
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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.
How Fluoxetine Affects Weight
Fluoxetine is not a weight loss drug—it's an SSRI (selective serotonin reuptake inhibitor) used to treat depression and anxiety. However, weight changes can occur as a side effect. Some people experience initial weight loss in the first few weeks, often due to reduced appetite or nausea. Others may experience weight gain over time, particularly if depression improves and appetite normalises, or if the medication affects metabolism slightly.
These effects vary considerably between individuals. Fluoxetine is prescribed based on mental health need, not weight management. If weight loss is your primary goal, prescription weight loss injections like Mounjaro (tirzepatide) and Wegovy (semaglutide) are the UK-licensed medications specifically designed for this purpose. Our free GLP-1 weight loss calculator can help you understand how these medications work and their potential outcomes.
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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.
UK Prescription Weight Loss Options
If you're seeking prescription weight loss medication in the UK, three licensed options are available: Mounjaro, Wegovy, and Saxenda. These are prescribed to adults with a BMI of 30 or above, or 27–29.9 with weight-related health conditions. Both NHS and private routes exist. Check your eligibility using our free BMI calculator above.
Access varies: NHS specialist weight management services have long waiting lists in many areas, whilst private prescribing offers faster access following an online clinical assessment. Your GP can discuss which route suits you best. Weight loss injections work alongside diet and physical activity—they're not replacements for lifestyle changes.
- 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 fluoxetine cause weight loss?
Fluoxetine can cause initial weight loss in some people (often due to reduced appetite), but weight gain is more common long-term. It's not a weight loss medication—it's prescribed for depression and anxiety. Weight changes are side effects, not the intended purpose.
What prescription weight loss medications are available in the UK?
Three are licensed: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). Mounjaro and Wegovy are once-weekly injections. All require a prescription and clinical assessment to confirm eligibility based on BMI and health status.
Can I get weight loss medication on the NHS in the UK?
Yes, but only through specialist tier 3 weight management services. Referral from your GP is required. Availability and waiting times vary significantly by region. Private prescribing offers faster access without an NHS referral.
Who is eligible for prescription weight loss medication in the UK?
Adults with a BMI of 30 or above, or 27–29.9 with weight-related conditions (diabetes, heart disease, high blood pressure). Lower thresholds apply for South Asian, Chinese, and Black African/Caribbean adults due to higher health risks at lower BMI.
How much weight can I expect to lose with Mounjaro or Wegovy?
Clinical trials showed average weight loss of 15–21% with Mounjaro and around 15% with Wegovy over several months. Results vary significantly between individuals. Success depends on medication dose, diet changes, and increased activity. Use our weight loss calculator to see potential projections.
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.