Tirzepatide (Mounjaro, Zepbound)

A once-weekly shot that acts on both GIP and GLP-1 receptors. Approved for type 2 diabetes, weight management and sleep apnea with obesity.

Evidence: Extensive clinical research
Half-life: ~5 days
Sources: 4 cited

Is tirzepatide FDA-approved?

FDA-approved as Mounjaro (2022, type 2 diabetes) and Zepbound (2023, weight management; 2024, sleep apnea with obesity). Compounded copies aren't FDA-approved.

Overview

Tirzepatide was the first approved medicine to switch on two gut-hormone receptors, GIP and GLP-1. It's sold as Mounjaro for type 2 diabetes and Zepbound for weight management. In the 72-week SURMOUNT-1 trial, adults with obesity on the highest dose lost about 21% of their body weight on average, versus about 3% on placebo.

How it works

The GLP-1 part lowers appetite, slows the stomach and helps insulin release. GIP is a second gut hormone that also boosts insulin after meals and seems to add to the effect on appetite and fat tissue. Hitting both receptors with one molecule gives more weight loss than GLP-1 alone in head-to-head trials.

How long does tirzepatide stay in the body?

About 5 days. Levels peak 8–72 hours after a shot and reach a steady level after about 4 weeks of weekly shots.

What it's studied for

Type 2 diabetes
Weight management
Obstructive sleep apnea
Heart failure with preserved ejection fraction
Fatty liver disease (MASH)

Reported side effects

Nausea, diarrhea, vomiting, constipation, indigestion, lower appetite
Can make birth-control pills less reliable for 4 weeks after starting and after each dose increase
Gallbladder problems and pancreatitis (rare)
Boxed warning: thyroid C-cell tumors seen in rodents. Not for people with a personal or family history of medullary thyroid cancer or MEN 2.

How should tirzepatide be stored?

Keep in the fridge (36–46°F / 2–8°C) and don't freeze. Single-dose pens or vials can stay unrefrigerated, up to 86°F (30°C), for up to 21 days.

Sources

The studies and prescribing labels this page is written from.