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
Best Time Of Day To Take Prozac For Weight Loss
Prozac (fluoxetine) is primarily an antidepressant and is not approved by the NHS or MHRA for weight loss in the UK. While some people notice weight changes when taking Prozac, it is not a weight management medication. If you're seeking prescription weight loss support in the UK, GLP-1 weight loss injections like Wegovy and Mounjaro are licensed alternatives that work through different mechanisms. This guide explains why Prozac isn't a weight loss treatment and what NHS-approved options are actually available for effective weight management.
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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.
Why Prozac Isn't A Weight Loss Medication
Prozac (fluoxetine) is a selective serotonin reuptake inhibitor (SSRI) antidepressant prescribed to treat depression, anxiety, and obsessive-compulsive disorder. It is not licensed or recommended for weight loss in the UK. Although some patients experience appetite changes while taking Prozac—either increased or decreased appetite—these are potential side effects, not the intended therapeutic effect.
Weight changes on Prozac are unpredictable and vary widely between individuals. Some people gain weight, others lose it, and many experience no change at all. The timing of your dose (morning or evening) does not significantly alter weight loss potential because Prozac is not designed to reduce body weight. If you are taking Prozac for depression or anxiety and have concerns about weight changes, always discuss this with your GP rather than adjusting your dose or timing yourself.
- Prozac is an antidepressant, not a weight management medication
- Weight changes are unpredictable side effects, not the primary action
- Timing of doses does not improve weight loss outcomes
- For intentional weight loss, prescription alternatives are more effective
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.
Prescription Weight Loss Options Available On The NHS
If you need prescription weight loss support in the UK, the NHS recommends GLP-1 weight loss injections and other licensed weight management medications. Wegovy (semaglutide) and Mounjaro (tirzepatide) are prescription-only weight management injections licensed in the UK. These work by activating hormone pathways that regulate appetite and support feeling fuller after smaller meals.
Clinical trials showed that Wegovy helps users lose an average of around 15% of body weight, whilst Mounjaro showed weight loss ranging from 15–21% depending on dose. Both require a prescription following a clinical assessment. Access through the NHS is via specialist weight management services (tier 3), though availability varies by region. Private online prescribing is also available through UK-licensed prescribers. Use our free GLP-1 weight loss calculator to explore potential outcomes with evidence-based alternatives.
- 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.
Is Prozac ever used for weight loss in the UK?
No. Prozac (fluoxetine) is not licensed or recommended for weight loss in the UK. It is prescribed for depression and anxiety. While weight changes can occur as a side effect, Prozac is not a weight management medication and should never be taken specifically for weight loss.
Does taking Prozac at a specific time help with weight loss?
No. The timing of your Prozac dose (morning or evening) does not affect weight loss because Prozac is not designed to reduce body weight. Weight changes are unpredictable side effects unrelated to dose timing. Always follow your GP's dosing instructions.
What prescription weight loss options are available in the UK?
The NHS prescribes licensed GLP-1 weight loss injections including Wegovy and Mounjaro for eligible adults. These are prescription-only medications requiring clinical assessment. They work through appetite regulation mechanisms and clinical trials showed significant weight loss results when combined with lifestyle changes.
Can I ask my GP to prescribe Prozac for weight loss?
No. Your GP will not prescribe Prozac for weight loss as it is not indicated for this purpose. If you need weight management support, discuss prescription weight loss medications or NHS weight management programmes with your GP instead. They can refer you to appropriate services.
How does GLP-1 weight loss medication work differently from Prozac?
GLP-1 injections like Wegovy activate natural hormone pathways that regulate appetite and glucose control—their primary mechanism is weight management. Prozac works on serotonin to treat depression; weight changes are incidental. GLP-1 medications are specifically designed and tested for weight loss.
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.