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
Prednisone and Weight Loss — What You Need to Know
Prednisone (a corticosteroid) is known to increase appetite and weight gain in many people taking it. While personal weight loss stories circulate online, the most effective approach in the UK is addressing weight through evidence-based methods alongside medical guidance. If you're concerned about weight changes related to prescription medication, your GP can discuss safe, clinically-proven weight management options available on the NHS or privately. This guide covers what NHS weight loss support looks like and who is eligible for prescription weight loss medication.
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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 Prescription Weight Loss Options
If you've gained weight during corticosteroid treatment and need support losing it, several prescription weight loss medications are available in the UK for eligible adults. These are not replacements for medical advice about your corticosteroid, but rather separate treatment options for weight management once your medication circumstances have stabilised.
The three main options are:
- Mounjaro (tirzepatide) — a once-weekly injection that activates two hormone pathways. Clinical trials showed an average weight loss of 15–21% of body weight over 72 weeks, though individual results vary significantly.
- Wegovy (semaglutide) — a once-weekly GLP-1 injection. In clinical trials, participants lost approximately 15% of body weight on average, alongside diet and activity changes.
- Saxenda (liraglutide) — a daily GLP-1 injection. Evidence supports modest weight loss when combined with lifestyle changes.
All three are prescription-only and require a clinical assessment by a licensed prescriber to confirm suitability. Eligibility typically requires a BMI of 30 or above, or 27 or above with weight-related health conditions such as high blood pressure or type 2 diabetes. Use our BMI calculator above to check where you stand, and our GLP-1 weight loss calculator to explore potential results at different doses.
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 Access — How to Get Started
NHS access: Referral to a tier 3 specialist weight management service through your GP. NICE has approved these medications for NHS use, though availability varies significantly by region and waiting times can be lengthy. Your GP can discuss eligibility and refer you if appropriate.
Private access: Available through GPhC-registered online prescribing services following an online clinical assessment. This route does not require NHS referral and medication is dispensed by a UK pharmacy. Costs typically range from £129–£320 per month depending on dose.
Whichever route you choose, weight loss medications work best alongside dietary changes and increased physical activity. Track your progress using our free progress tracker to monitor both weight changes and how you're feeling on your chosen approach.
- 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 I take weight loss injections while on prednisone?
This requires individual assessment by your prescriber. Some people do take both, but your doses and timing may need adjustment. Always inform any new prescriber about all your current medications, including corticosteroids. Your GP should coordinate care between specialists managing both your corticosteroid treatment and any weight loss medication.
What is the difference between Mounjaro and Wegovy?
Mounjaro (tirzepatide) activates two hormone pathways (GIP and GLP-1), while Wegovy (semaglutide) activates one (GLP-1 only). Clinical trials suggest Mounjaro may produce slightly greater average weight loss (15–21% vs approximately 15%), but individual results vary. Both are once-weekly injections. Your prescriber will recommend based on your personal health profile.
How quickly will I lose weight on these medications?
Weight loss typically becomes noticeable around week 4–6, but builds gradually over months. Clinical trials measured results over 68–72 weeks. Average weight loss is 0.5–1 kg per week, though this varies between individuals based on dose, diet, activity, and metabolism. Patience and consistency with lifestyle changes are key.
Can I get weight loss injections on the NHS?
Yes. NICE has approved Mounjaro, Wegovy, and Saxenda for NHS use in specialist tier 3 weight management services. However, availability varies significantly by region (ICB). Ask your GP about referral options in your area. Some regions have longer waiting lists than others.
What if I'm not eligible for prescription weight loss medication?
The NHS offers free support through tier 1 and 2 services, including digital weight loss programmes, community support groups, and behaviour change interventions. Apps, online tools like our weight converter and BMI calculator, and structured diet programmes can all support gradual, sustainable weight loss without medication.
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.