Semaglutide vs Tirzepatide: GLP-1 Comparison Guide

What are GLP-1 medications?

GLP-1 (glucagon-like peptide-1) receptor agonists are prescription medications that mimic a natural gut hormone released after eating. They slow gastric emptying, reduce appetite, and improve blood sugar control. Originally developed to treat type 2 diabetes, GLP-1s have become one of the most effective clinical tools for chronic weight management.

The two most-prescribed options in the U.S. today are Semaglutide (brand names Ozempic and Wegovy) and Tirzepatide (brand names Mounjaro and Zepbound). Both are once-weekly injections. The key difference: Tirzepatide is a dual GIP/GLP-1 agonist, which appears to drive greater average weight loss in clinical trials.

Side-by-side comparison

Efficacy: what the trials show

In the pivotal STEP-1 trial, adults with obesity taking Semaglutide 2.4 mg lost an average of 14.9% of body weight over 68 weeks, compared with 2.4% in the placebo group. In SURMOUNT-1, adults taking Tirzepatide 15 mg lost an average of 20.9% over 72 weeks, with more than half of participants losing at least 20% of their starting weight.

Tirzepatide's dual mechanism — acting on both GIP and GLP-1 receptors — appears to translate to greater average weight loss in head-to-head observational data. That said, real-world response varies. Many patients reach their goals on Semaglutide alone; others do better on Tirzepatide, or need to switch based on tolerability, cost, or availability.

Dosing and titration

Both medications are titrated slowly to minimize side effects. Semaglutide typically starts at 0.25 mg weekly and increases every four weeks toward a target of 2.4 mg. Tirzepatide starts at 2.5 mg weekly and can be titrated up to 15 mg over about 20 weeks. Your provider will adjust the schedule based on tolerance and clinical response.

Side effects and safety

The most common side effects for both medications are gastrointestinal — nausea, diarrhea, constipation, and reflux. These are usually mild to moderate and improve as your body adjusts. Slow titration, adequate hydration, and smaller lower-fat meals help most patients push through the first few weeks.

Both medications carry a boxed warning about the risk of thyroid C-cell tumors observed in rodent studies. They are not recommended for people with a personal or family history of medullary thyroid carcinoma or Multiple Endocrine Neoplasia syndrome type 2. Rare but serious risks include pancreatitis, gallbladder disease, and severe hypoglycemia (especially when combined with insulin or sulfonylureas).

How to choose

The right medication depends on your health history, weight loss goals, insurance, and how your body responds. In general:

• Semaglutide may be a good starting point if you have a longer track record of clinical use, want a well-studied option, or your insurance covers Wegovy.
• Tirzepatide may be preferred when higher average weight loss is a priority, or when a patient has plateaued on Semaglutide.
• Both require a licensed provider to evaluate whether you're an appropriate candidate — GLP-1s are prescription medications, not over-the-counter supplements.