Which Injection Causes More Side Effects: Mounjaro vs Ozempic
Both Mounjaro (tirzepatide) and Ozempic (semaglutide) have similar overall side effect profiles, with gastrointestinal adverse events being the most common for both medications, though tirzepatide at higher doses (10-15 mg) shows slightly higher rates of nausea and vomiting compared to semaglutide 1 mg. 1
Gastrointestinal Side Effects
The most frequent adverse events for both medications are gastrointestinal in nature and are primarily mild to moderate in severity:
- Tirzepatide (5-15 mg): Nausea occurs in 17-22% of patients, diarrhea in 13-16%, and vomiting in 6-10% 1
- Semaglutide (1 mg): Nausea occurs in 18% of patients, diarrhea in 12%, and vomiting in 8% 1
The gastrointestinal side effect rates are remarkably similar between the two medications, with tirzepatide showing only marginally higher rates at the highest doses. 1 Both medications cause delayed gastric emptying as a class effect that may persist with chronic use. 2
Hypoglycemia Risk
Both medications have low hypoglycemia risk when used appropriately:
- Tirzepatide: Severe hypoglycemia (blood glucose <54 mg/dL) occurred in 0.6% (5 mg), 0.2% (10 mg), and 1.7% (15 mg) of patients 1
- Semaglutide: Severe hypoglycemia occurred in 0.4% of patients 1
The hypoglycemia risk is minimal for both medications when used as monotherapy or with metformin, but increases substantially when combined with insulin or sulfonylureas. 2 When adding either medication to insulin therapy, insulin dose reduction is necessary to minimize hypoglycemia risk. 2
Serious Adverse Events
The overall serious adverse event rates differ slightly:
- Tirzepatide: Serious adverse events were reported in 5-7% of patients 1
- Semaglutide: Serious adverse events were reported in 3% of patients 1
However, when compared to usual care in network meta-analyses, both GLP-1 agonists (including semaglutide) and tirzepatide showed reductions in serious adverse events compared to insulin, with tirzepatide showing a relative risk of 0.79 compared to insulin. 2
Key Safety Considerations
Both medications share similar contraindications and monitoring requirements:
- Personal or family history of medullary thyroid cancer or MEN2 3
- History of pancreatitis (use with caution) 3
- Risk of acute gallbladder disease 3
- Monitoring for suicidal ideation and behavior 3
Clinical Context
In head-to-head comparison, tirzepatide demonstrated superior glycemic control and weight loss compared to semaglutide 1 mg, but the safety profiles remained comparable. 1 The slightly higher rates of gastrointestinal side effects with tirzepatide at higher doses (15 mg) are offset by its greater efficacy in weight reduction and HbA1c lowering. 4
Neither medication increases the risk of severe hypoglycemia when used appropriately, and both consistently reduce severe hypoglycemia compared to insulin or sulfonylureas. 3 The choice between these medications should prioritize the patient's need for glycemic control and weight loss rather than side effect differences, as the safety profiles are largely equivalent. 1, 4