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
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Mounjaro and Steroids — How They Differ for Weight Management
If you're exploring weight management options in the UK, you may have encountered both Mounjaro and steroid-based approaches. These are fundamentally different medicines with different mechanisms, uses, and health effects. Mounjaro (tirzepatide) is a prescription-only GIP and GLP-1 receptor agonist designed specifically for weight management in eligible adults. Steroids, by contrast, are corticosteroids typically prescribed for inflammatory or autoimmune conditions — not for weight loss. This guide explains the key differences, how they work, and which might be appropriate for your situation.
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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 Mounjaro and Steroids Work Differently
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist. It activates two natural hormone pathways to help regulate appetite, reduce food cravings, and support feeling fuller after meals. It also slows gastric emptying and helps regulate fat utilisation. When used with a reduced-calorie diet and increased physical activity, clinical trials (SURMOUNT-1) showed Mounjaro helped participants lose an average of 15–21% of body weight — though individual results vary significantly.
Steroids (corticosteroids) like prednisolone or dexamethasone are anti-inflammatory medications prescribed for conditions such as rheumatoid arthritis, asthma, or inflammatory bowel disease. They are not weight loss drugs. In fact, long-term steroid use often causes weight gain as a side effect, increased appetite, fluid retention, and redistribution of body fat — the opposite of what you would want for weight management.
The key difference: Mounjaro targets appetite regulation specifically for weight loss, while steroids target inflammation and immune function. They serve completely different purposes.
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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.
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Which Is Right for You? Prescription and Eligibility
Both Mounjaro and any steroid medication are prescription-only in the UK and require clinical assessment by a qualified healthcare professional.
Mounjaro eligibility (weight management): Adults with a BMI of 30 kg/m² or above, or 27–29.9 kg/m² with weight-related health conditions (type 2 diabetes, high blood pressure, cardiovascular disease, or sleep apnoea). Available through NHS specialist tier 3/4 weight management services or private prescribing following online assessment.
Steroids (if prescribed) are prescribed only when you have a medical condition that requires them — not for weight loss. If you're taking steroids for a medical condition and experiencing weight gain, speak to your GP about managing side effects alongside the underlying condition.
Your GP or a licensed prescriber can assess whether Mounjaro (or any medication) is suitable for you based on your individual health profile, medical history, and weight management goals.
- 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 Mounjaro a steroid?
No. Mounjaro (tirzepatide) is a GIP and GLP-1 receptor agonist — it works on appetite-regulating hormone pathways. Steroids are corticosteroids used for inflammation and immune conditions. They are entirely different drug classes with different mechanisms and uses.
Can steroids be used for weight loss?
No. Steroids are not prescribed for weight loss and typically cause weight gain as a side effect, particularly with long-term use. If you're taking steroids for a medical condition, speak to your GP about managing weight-related side effects safely.
Does Mounjaro have steroid side effects?
No. Mounjaro is not a steroid and does not carry steroid-related risks like immunosuppression or bone weakening. Common Mounjaro side effects are gastrointestinal (nausea, diarrhoea, vomiting, constipation) — not steroid-related effects.
How do I know if Mounjaro is right for me?
Mounjaro requires a clinical assessment by a UK-licensed prescriber or NHS weight management service. Eligibility depends on your BMI, health conditions, and weight management goals. Use our free BMI calculator and GLP-1 weight loss calculator to understand your starting point, then speak to your GP.
What if I'm taking steroids and want to lose weight?
If you're on steroids for a medical condition and experiencing weight gain, do not stop taking steroids without medical guidance — they're treating your underlying condition. Instead, speak to your GP about safe weight management strategies, dietary support, and whether medicines like Mounjaro might be suitable alongside your current treatment.
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.