Tirzepatide: FDA Approvals, SURMOUNT & SURPASS Trials

What tirzepatide is

Tirzepatide is a once-weekly injectable that activates two incretin receptors at once: the glucose-dependent insulinotropic polypeptide (GIP) receptor and the glucagon-like peptide-1 (GLP-1) receptor. Semaglutide targets GLP-1 alone; adding GIP activity is what makes tirzepatide a distinct molecule rather than another single-pathway GLP-1 drug. It is sold by Eli Lilly as Mounjaro for type 2 diabetes and as Zepbound for weight management, and it has an elimination half-life of roughly five days, which supports weekly dosing.

FDA approval timeline

May 2022

Mounjaro approved

FDA approves tirzepatide for adults with type 2 diabetes

Nov 2023

Zepbound approved

Approved for chronic weight management in obesity or overweight with a weight-related condition

Dec 2024

Sleep apnea indication

Zepbound approved for moderate-to-severe obstructive sleep apnea in adults with obesity, based on SURMOUNT-OSA

The trial evidence

SURPASS-2 — diabetes, head-to-head vs semaglutide

In adults with type 2 diabetes, tirzepatide produced larger A1c reductions than semaglutide 1 mg across its 5, 10, and 15 mg doses, with greater weight loss as well.

Source: Frías JP, et al. "Tirzepatide versus Semaglutide Once Weekly in Type 2 Diabetes." N Engl J Med. 2021.

SURMOUNT-1 — weight management

Population: 2,539 adults with obesity or overweight, without diabetes
Duration: 72 weeks
Mean weight change: about −15% (5 mg), −19.5% (10 mg), and −20.9% (15 mg), versus roughly −3% on placebo

Source: Jastreboff AM, et al. "Tirzepatide Once Weekly for the Treatment of Obesity." N Engl J Med. 2022.

A later head-to-head weight-management trial (SURMOUNT-5) reported greater average weight loss with tirzepatide than with semaglutide 2.4 mg. Direct comparisons still depend on dose, duration, and population, so they inform the picture rather than settle it.

Dosing and approved uses

Product	Indication	Approved	Dose range
Mounjaro	Type 2 diabetes	2022	2.5–15 mg weekly
Zepbound	Weight management; obstructive sleep apnea in obesity	2023 / 2024	2.5–15 mg weekly

Dosing starts low (2.5 mg) and steps up over months to limit gastrointestinal side effects. The most common adverse effects are nausea, diarrhea, vomiting, and constipation, usually strongest during dose escalation.

Safety notes

Carries a boxed warning for thyroid C-cell tumors based on rodent studies; contraindicated with a personal or family history of medullary thyroid carcinoma or MEN 2.
Reported risks include pancreatitis, gallbladder disease, and — as with other agents that slow gastric emptying — considerations around anesthesia and delayed stomach emptying.
Compounded tirzepatide is not the same as the approved product; quality and dosing accuracy have been the subject of FDA warnings.

Keep reading: Semaglutide vs. tirzepatide, our GLP-1 side-effect guide, and what to know about compounded tirzepatide.

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