Common Dosage
2.5mg weekly (titrated up)
Category
Weight Loss
- Significant weight loss
- Improved insulin sensitivity
- Appetite control
Tirzepatide (branded as Mounjaro for diabetes and Zepbound for obesity) was developed by Eli Lilly and received FDA approval in 2022 for type 2 diabetes and 2023 for weight management. It represents a significant advance over semaglutide by simultaneously activating both GLP-1 and GIP (glucose-dependent insulinotropic polypeptide) receptors. The SURMOUNT trial program generated substantial excitement in obesity medicine by showing superior weight loss to any previously approved medication.
As a dual GIP/GLP-1 receptor agonist, tirzepatide leverages two complementary hormonal pathways. GLP-1 activation suppresses appetite and slows gastric emptying. GIP activation enhances insulin secretion in a glucose-dependent manner and may play a role in adipocyte metabolism and energy expenditure. The synergistic effect appears to be greater than either pathway alone, potentially explaining the superior weight loss compared to GLP-1-only agents.
- Weight management — achieving up to 22.5% body weight reduction in clinical trials
- Type 2 diabetes management with superior HbA1c reduction vs. semaglutide
- Non-alcoholic fatty liver disease (NAFLD/NASH) — reducing hepatic steatosis
- Obstructive sleep apnea — SURMOUNT-OSA demonstrated significant AHI reduction
- Cardiovascular risk reduction — SURPASS-CVOT trial ongoing
- Insulin resistance and metabolic syndrome
SURMOUNT-1 Trial
The landmark SURMOUNT-1 trial (n=2539) showed average weight loss of 20.9% at the 15mg dose over 72 weeks, with one-third of participants losing ≥25% of body weight. These results exceeded any previously observed pharmacological weight loss outcomes without surgical intervention.
Head-to-Head vs. Semaglutide
The SURPASS-2 trial directly compared tirzepatide to semaglutide 1mg in T2D patients. Tirzepatide at all doses (5, 10, 15mg) produced greater HbA1c reductions and weight loss than semaglutide, with the 15mg dose showing approximately 3kg greater weight loss.
Sleep Apnea Improvement
The SURMOUNT-OSA trial demonstrated ~63% reduction in apnea-hypopnea index (AHI) in non-CPAP users with moderate-to-severe OSA — a clinically meaningful result that led to an FDA approval expansion for this indication in 2024.
- Similar GI side effect profile to semaglutide — nausea, diarrhea, vomiting are most common
- Same thyroid carcinoma black box warning as GLP-1 class medications
- Cost and access barriers — pharmaceutical-grade tirzepatide is expensive without insurance
- Lean mass loss parallels fat loss — protein intake and strength training are critical
- Rebound weight gain risk on discontinuation is similar to semaglutide
- Research-grade compounded versions carry uncertain dosing and sterility standards
- Nausea
- Gastrointestinal discomfort