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Is Mounjaro a steroid? This is a common question amongst patients considering this medication for weight management or type 2 diabetes. Mounjaro (tirzepatide) is definitively not a steroid. It is a peptide-based medication that works by mimicking naturally occurring gut hormones to regulate appetite and blood glucose levels. Unlike corticosteroids or anabolic steroids, which have entirely different chemical structures and mechanisms of action, Mounjaro belongs to a class of medicines called dual GIP and GLP-1 receptor agonists. Understanding this fundamental difference is essential for patients and healthcare professionals when considering treatment options and managing expectations regarding therapeutic effects and potential side effects.
Quick Answer: Mounjaro (tirzepatide) is not a steroid; it is a peptide-based medication that mimics gut hormones to regulate appetite and blood glucose.
Mounjaro (tirzepatide) is a prescription medicine approved in the UK for the treatment of type 2 diabetes and for weight management in adults with obesity or overweight with weight-related health conditions. It belongs to a class of medications known as dual glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) receptor agonists.
The medication works by mimicking two naturally occurring hormones in the body that regulate appetite and blood sugar levels. When administered as a once-weekly subcutaneous injection, tirzepatide activates both GIP and GLP-1 receptors in the pancreas, brain, and gastrointestinal tract. This dual action enhances insulin secretion when blood glucose levels are elevated, suppresses glucagon release (which normally raises blood sugar), and slows gastric emptying. These mechanisms collectively reduce appetite and increase feelings of fullness after eating.
Key pharmacological effects include:
Reduced food intake through central appetite suppression
Delayed gastric emptying, prolonging satiety
Improved insulin sensitivity and glucose metabolism
Unlike medications that work through stimulant effects or fat absorption inhibition, Mounjaro's mechanism is hormone-based and targets the body's natural regulatory pathways. The medication requires gradual dose escalation with increases no more frequently than every 4 weeks to minimise gastrointestinal side effects and optimise therapeutic response.
Clinical trials have demonstrated significant weight loss, with results varying by dose and whether patients have diabetes. In the SURMOUNT trials for weight management, participants without diabetes typically achieved greater weight loss than those with type 2 diabetes. Mounjaro should not be used in patients with type 1 diabetes or diabetic ketoacidosis, and should not be used alongside other GLP-1 receptor agonists.
References:
MHRA/EMC Summary of Product Characteristics: Mounjaro (tirzepatide)
NICE Technology Appraisal: Tirzepatide for managing overweight and obesity
NICE NG28: Type 2 diabetes in adults: management
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Understanding the side effect profile of Mounjaro is essential for patients and healthcare professionals, particularly when distinguishing it from steroid medications, which have an entirely different adverse effect spectrum.
Common side effects of Mounjaro include:
Gastrointestinal disturbances – nausea, vomiting, diarrhoea, constipation, and abdominal discomfort are the most frequently reported adverse effects, typically occurring during dose escalation and often improving with continued use
Reduced appetite – whilst therapeutically desired, some patients experience excessive appetite suppression
Injection site reactions – mild redness, itching, or discomfort at the injection site
Fatigue and dizziness – particularly during the initial treatment period
Hypoglycaemia – mainly a risk when used with insulin or sulfonylureas, which may require dose adjustment of these medications
More serious but less common risks include:
Gallbladder disease (cholelithiasis, cholecystitis)
Dehydration potentially leading to acute kidney injury
Pancreatitis
Severe hypersensitivity reactions
Potential worsening of diabetic retinopathy in people with diabetes, particularly with rapid improvement in blood glucose control
In contrast, corticosteroid medications (such as prednisolone or dexamethasone) produce markedly different side effects, particularly with prolonged use. These include weight gain, fluid retention, increased appetite, mood changes, elevated blood pressure, increased infection risk, osteoporosis, skin thinning, and metabolic disturbances including hyperglycaemia. Steroids suppress the immune system and affect multiple organ systems through their anti-inflammatory and immunosuppressive actions.
Patients should seek urgent medical attention if they experience:
Severe, persistent abdominal pain, especially if radiating to the back (possible pancreatitis)
Persistent vomiting/diarrhoea with reduced urine output (dehydration/acute kidney injury)
Jaundice or right upper quadrant pain (possible gallbladder disease)
Signs of severe allergic reaction (facial swelling, breathing difficulty, rash)
New or worsening visual symptoms (for people with diabetes)
Suspected side effects should be reported via the MHRA Yellow Card scheme (yellowcard.mhra.gov.uk or the Yellow Card app).
References:
MHRA/EMC Summary of Product Characteristics: Mounjaro (tirzepatide)
EMA European Public Assessment Report: Mounjaro (tirzepatide)
NHS medicines information: GLP-1 receptor agonists
Access to Mounjaro on the NHS is governed by NICE guidance and specific eligibility criteria that reflect evidence-based prescribing for appropriate patient populations. Mounjaro is indicated only for adults and is not established for use in children or adolescents.
For weight management, NICE eligibility criteria include:
Body Mass Index (BMI) ≥35 kg/m² with at least one weight-related comorbidity (such as type 2 diabetes, hypertension, obstructive sleep apnoea, or cardiovascular disease), OR
BMI ≥30 kg/m² in certain circumstances, particularly for individuals with type 2 diabetes where weight loss would provide significant metabolic benefit
Evidence of previous attempts at weight management through lifestyle interventions (dietary modification and increased physical activity)
Commitment to ongoing lifestyle changes and regular monitoring
For individuals of South Asian, Chinese, other Asian, Middle Eastern, Black African, or African-Caribbean family background, lower BMI thresholds may apply (typically 2.5 kg/m² lower) due to increased cardiometabolic risk at lower body weights.
Precautions and considerations include:
Personal or family history of medullary thyroid carcinoma or Multiple Endocrine Neoplasia syndrome type 2 (requires careful risk assessment)
Severe gastrointestinal disease
Pregnancy or breastfeeding (use is not recommended; effective contraception advised)
History of pancreatitis requires careful risk-benefit assessment
Women using oral contraceptives should use additional or alternative contraception for 4 weeks after starting Mounjaro and for 4 weeks after each dose increase due to potential reduced contraceptive effectiveness
Should not be used with other GLP-1 receptor agonists
NHS prescribing typically requires specialist initiation through weight management services or diabetes clinics, with ongoing monitoring of weight loss response, tolerability, and metabolic parameters. Treatment continuation is usually reviewed at specified intervals, with discontinuation recommended if insufficient weight loss is achieved according to NICE criteria. Private prescribing is also available but involves significant out-of-pocket costs. Patients should discuss their individual circumstances with their GP or specialist to determine eligibility and appropriateness of treatment.
References:
NICE Technology Appraisal: Tirzepatide for managing overweight and obesity
NICE NG28: Type 2 diabetes in adults: management
MHRA/EMC Summary of Product Characteristics: Mounjaro (tirzepatide)
Faculty of Sexual and Reproductive Healthcare (FSRH) CEU statement on GLP-1 receptor agonists and oral contraception
No, Mounjaro is definitively not a steroid. This is a common misconception that requires clarification, as the two medication classes are fundamentally different in their chemical structure, mechanism of action, therapeutic uses, and side effect profiles.
Mounjaro (tirzepatide) is a peptide-based medication – specifically, a synthetic analogue of naturally occurring gut hormones. Its molecular structure consists of a modified 39-amino acid peptide chain that mimics GIP and GLP-1. It works by binding to specific receptors in the body that regulate appetite, glucose metabolism, and energy balance. Mounjaro does not have any steroid structure or steroid-like activity.
Steroids, by contrast, are a broad class of compounds with a characteristic four-ring chemical structure. In medical contexts, "steroids" typically refers to:
Corticosteroids (such as prednisolone, hydrocortisone, dexamethasone) – synthetic versions of cortisol used for anti-inflammatory and immunosuppressive effects
Anabolic steroids (such as testosterone derivatives) – used for hormone replacement or, illicitly, for muscle building
These medications work through entirely different mechanisms, binding to intracellular steroid receptors and affecting gene transcription across multiple organ systems.
Key differences include:
Chemical structure – Mounjaro is a peptide; steroids are lipid-based hormones
Mechanism – Mounjaro activates cell surface receptors; steroids work through nuclear receptors
Therapeutic use – Mounjaro for weight/diabetes management; steroids for inflammation, immune suppression, or hormone replacement
Side effects – Completely different profiles reflecting distinct mechanisms
Regulatory classification – Different drug classes under MHRA regulation
The confusion may arise because both are injectable medications used for chronic conditions, but there is no pharmacological or chemical relationship between Mounjaro and steroid medications. Understanding this distinction is important for informed treatment decisions and appropriate expectations regarding therapeutic effects and potential adverse reactions. Patients with concerns about their medication should discuss them with their prescribing clinician or pharmacist.
References:
MHRA/EMC Summary of Product Characteristics: Mounjaro (tirzepatide)
EMA European Public Assessment Report: Mounjaro (tirzepatide)
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, a peptide-based medication that mimics naturally occurring gut hormones to regulate appetite and blood glucose levels. It is not a steroid and has no steroid-like structure or activity.
Mounjaro may be available on the NHS for weight management if you meet NICE eligibility criteria, including BMI ≥35 kg/m² with weight-related comorbidity or BMI ≥30 kg/m² in certain circumstances. Specialist initiation through weight management services or diabetes clinics is typically required.
The most common side effects of Mounjaro are gastrointestinal disturbances including nausea, vomiting, diarrhoea, constipation, and abdominal discomfort, particularly during dose escalation. These typically improve with continued use and differ entirely from steroid side effects such as weight gain and immune suppression.
All medical content on this blog is created based on reputable, evidence-based sources and reviewed regularly for accuracy and relevance. While we strive to keep content up to date with the latest research and clinical guidelines, it is intended for general informational purposes only.
DisclaimerThis content is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare professional with any medical questions or concerns. Use of the information is at your own risk, and we are not responsible for any consequences resulting from its use.
