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
Does Spironolactone Cause Weight Loss?
Spironolactone is a potassium-sparing diuretic prescribed for high blood pressure and fluid retention, not for weight loss. Some people may experience modest weight changes while taking it, but this isn't its primary purpose. If you're looking for weight management in the UK, prescription weight loss medications are specifically designed and licensed for this goal. This guide explains how spironolactone affects weight and introduces evidence-based prescription weight loss options available to eligible adults.
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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 Spironolactone Affects Weight
Spironolactone works by blocking aldosterone, a hormone that regulates salt and fluid balance in the body. By reducing fluid retention, some patients notice a modest decrease in overall weight—typically 1–3 kg—because they're losing excess water, not fat. This is not the same as fat loss and is not why the medication is prescribed.
Spironolactone is approved in the UK for managing high blood pressure and polycystic ovary syndrome (PCOS), where it can help regulate hormones and reduce bloating. Any weight change is a secondary effect, not a therapeutic goal. Your GP may prescribe it for these conditions, but if your primary concern is weight management, you should discuss prescription weight loss options instead.
- Weight loss with spironolactone is typically fluid loss, not fat loss
- It's prescribed for blood pressure and PCOS, not weight management
- Results vary and are not assured
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.
UK-Licensed Prescription Weight Loss Options
If you're concerned about your weight, the NHS and private prescribers in the UK offer licensed prescription weight loss medications specifically designed for this purpose. These include Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide)—all approved by the MHRA for weight management.
Adults with a BMI of 30 or above, or 27 or above with weight-related health conditions such as type 2 diabetes or high blood pressure, may be eligible. Clinical trials show these medications help patients lose an average of 15–21% of their body weight when combined with lifestyle changes. Your GP can assess your eligibility or you can access private consultations with UK-licensed prescribers. Calculate your BMI instantly using our free BMI calculator above, and explore potential weight loss outcomes with our GLP-1 weight loss calculator.
- 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 spironolactone help me lose weight?
Spironolactone may cause modest weight reduction through fluid loss, but it's not prescribed for weight management. If weight loss is your goal, prescription weight loss medications like Mounjaro or Wegovy are specifically licensed for this and offer more substantial evidence-based results.
What are the main UK prescription weight loss options?
Mounjaro, Wegovy, and Saxenda are MHRA-approved for weight management in the UK. Mounjaro and Wegovy are once-weekly injections; Saxenda is a daily injection. All require a prescription and clinical assessment of your eligibility.
Who is eligible for prescription weight loss medication in the UK?
You may be eligible if you have a BMI of 30 or above, or 27–29.9 with weight-related conditions like type 2 diabetes, high blood pressure, or sleep apnoea. Your GP or a licensed prescriber can assess your suitability.
Can I get weight loss medication on the NHS?
Yes. The NHS funds prescription weight loss treatment through specialist tier 3 weight management services. Access varies by region and there may be waiting lists. Your GP can refer you, or you can seek private prescriptions for faster access.
How much weight can I expect to lose with prescription weight loss medication?
Clinical trials show patients lose an average of 15–21% of their body weight over 68–72 weeks alongside reduced-calorie diet and increased activity. Individual results vary significantly. Use our free weight loss calculator to explore potential outcomes.
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.