Zepbound vs Mounjaro

Zepbound and Mounjaro both contain tirzepatide, a once‑weekly injectable GIP/GLP‑1 receptor agonist made by Eli Lilly. The only distinction is their FDA approval:

• Zepbound is approved for chronic weight management in adults with obesity (BMI ≥ 30) or overweight (BMI ≥ 27) plus one weight‑related condition.
• Mounjaro is approved for improving blood sugar control in adults with type 2 diabetes.

Why two brands?

Mounjaro has been used off‑label for weight loss. Following the Ozempic→Wegovy model, Zepbound was introduced after the SURMOUNT‑1 trial showed > 20% average weight loss over 72 weeks at the highest dose.

How they work

Tirzepatide mimics GLP‑1 and GIP hormones to:

• Slow gastric emptying and reduce appetite
• Increase insulin release and lower blood sugar

Shared side effects

• Gastrointestinal: nausea, diarrhea, vomiting, indigestion, constipation
• Other: decreased appetite, burping, fatigue, stomach pain, hair loss, injection site reactions, dizziness

Serious risks (seek immediate care):

• Allergic reactions (hives, throat/tongue swelling, breathing difficulty)
• Pancreatitis (severe abdominal pain)
• Kidney injury (dehydration symptoms)
• Gallbladder issues (upper abdominal pain, fever)
• Hypoglycemia when combined with insulin or sulfonylureas
• Diabetic retinopathy worsening
• Thyroid tumors (lump in neck)
• Suicidal thoughts or depression

Boxed warning

• Avoid if personal/family history of medullary thyroid carcinoma or MEN 2 syndrome

Key differences

• Indication: Zepbound for weight loss; Mounjaro for type 2 diabetes
• Dosing: Both start at 2.5 mg weekly, titrated up to 15 mg
• Cost & savings: Similar list price (~$1,300/month); Lilly offers assistance programs

Switching brands

Because the active ingredient and dosing pens are identical, you may maintain your current dose when switching. Always consult your provider for guidance.

Sources

• Medscape: tirzepatide overview. Accessed 2025.
• DailyMed: Zepbound & Mounjaro prescribing information. Accessed 2025.
• Forbes: tirzepatide and blood pressure study. Accessed 2024.