Mounjaro (tirzepatide) and its weight-loss branded version Zepbound have become popular treatments for type 2 diabetes and obesity. While highly effective for many, these medications aren't appropriate for everyone. Understanding the contraindications and precautions can help you make an informed decision with your healthcare provider.
Absolute Contraindications
Do NOT take Mounjaro/Zepbound if you have:
- ✗Personal or family history of medullary thyroid carcinoma (MTC) — Like all GLP-1 drugs, tirzepatide carries a boxed warning about thyroid tumors
- ✗Multiple Endocrine Neoplasia syndrome type 2 (MEN 2) — This genetic condition significantly increases thyroid cancer risk
- ✗Known hypersensitivity to tirzepatide — Previous allergic reaction to the medication or any of its components
Conditions Requiring Careful Consideration
History of Pancreatitis
GLP-1 medications have been associated with acute pancreatitis. If you've had pancreatitis before, your doctor may recommend against Mounjaro or suggest extra monitoring.
Severe Gastrointestinal Disease
Conditions like gastroparesis, inflammatory bowel disease, or severe GERD may be worsened by tirzepatide's effects on gastric emptying.
Diabetic Retinopathy
Rapid blood sugar improvements can temporarily worsen diabetic eye disease. If you have retinopathy, more frequent eye exams may be needed.
Kidney Disease
While tirzepatide doesn't require dose adjustment for kidney disease, dehydration from GI side effects can worsen kidney function. Close monitoring is recommended.
Gallbladder Disease
Rapid weight loss increases gallstone risk. If you have existing gallbladder problems, discuss this with your provider. See our article onGLP-1s and gallstones.
Who Should Not Take Mounjaro
Pregnant or Planning Pregnancy
Tirzepatide should not be used during pregnancy:
- Animal studies showed adverse effects on fetal development
- Stop Mounjaro at least 1 month before trying to conceive
- Use reliable contraception while taking the medication
- Contact your doctor immediately if you become pregnant
Breastfeeding Mothers
It's unknown whether tirzepatide passes into breast milk. Due to lack of safety data, Mounjaro is not recommended while nursing.
Type 1 Diabetics
Mounjaro is NOT approved for type 1 diabetes. It works by enhancing insulin secretion from the pancreas—which doesn't help when the pancreas can't produce insulin.
Children and Adolescents
Mounjaro and Zepbound are currently approved only for adults (18+). Safety and efficacy haven't been established in pediatric populations.
How Mounjaro Differs from Ozempic
Mounjaro works on both GLP-1 and GIP receptors (dual agonist), while Ozempic only targets GLP-1. This difference means:
- Mounjaro typically produces greater weight loss (20-25% vs 15%)
- Side effect profiles are similar but may differ in intensity
- If you can't tolerate one, you might tolerate the other
- The same contraindications generally apply to both
Drug Interactions
Mounjaro can affect how other medications work:
| Medication | Concern |
|---|---|
| Insulin/Sulfonylureas | Increased hypoglycemia risk—doses may need reduction |
| Oral Contraceptives | Delayed absorption may reduce effectiveness |
| Oral Medications | Absorption timing may be affected by delayed gastric emptying |
The Bottom Line
Mounjaro/Zepbound is a powerful medication with impressive results for many people. However, it's not suitable for everyone. The contraindications exist to protect you from potentially serious complications. Always have a complete conversation with your healthcare provider about your medical history before starting any new medication.