Tirzepatide: Mechanism, Approval & SA Status

Tirzepatide activates two incretin receptors instead of one — GIP (glucose-dependent insulinotropic polypeptide) and GLP-1 — which is why it's sometimes called a "twincretin." It's approved by prescription for type 2 diabetes, weight management and obstructive sleep apnea, and it's also sold, unregulated, as a research peptide in the same online market as semaglutide.

How it works

Like semaglutide, tirzepatide activates the GLP-1 receptor — glucose-dependent insulin release, slowed gastric emptying, increased satiety. But it also activates the GIP receptor, which plays its own role in insulin secretion and appears to work synergistically with the GLP-1 pathway on fat tissue and metabolism. That dual mechanism is the basis for tirzepatide's approvals and is the main mechanistic difference from semaglutide's single-receptor action.

Approval history

May 2022: approved as Mounjaro for glycemic control in type 2 diabetes.
November 8, 2023: approved as Zepbound for chronic weight management in adults with obesity, or overweight with a weight-related condition.
December 20, 2024: Zepbound's approval extended to moderate-to-severe obstructive sleep apnea in adults with obesity — the first medication approved specifically for OSA.

Source: FDA-approved prescribing information for Zepbound (tirzepatide) injection, accessdata.fda.gov (label 217806, original approval 2023).

What's different from semaglutide, practically

Both compounds are once-weekly injectables approved for overlapping indications (type 2 diabetes, chronic weight management), and both carry similar gastrointestinal side-effect profiles and the same class-wide boxed warning about thyroid C-cell tumors seen in rodent studies. The dual GIP/GLP-1 mechanism is the reason tirzepatide is often discussed as the more potent of the two in head-to-head comparisons — but exact outcomes vary by dose, trial and individual, and neither drug's trial results translate to an unsupervised, unprescribed product.

South Africa status: the same regulatory gap applies here as with semaglutide. South Africa's medicines regulator, SAHPRA, requires registration for any product intended to treat or alter a bodily function, and has publicly warned against unregistered peptide products sold online and through informal channels. A pharmacy-dispensed, prescribed medicine is not the same product — legally or in terms of what's actually verified about its contents — as an unregulated vial marketed as "research-grade tirzepatide." See how we rate for the fuller regulatory picture.

See our vendor comparison for how vendors selling compounds like this document their own testing and sourcing claims.

This page is educational information about a molecule and its regulatory history. It is not medical advice, not a recommendation to use tirzepatide outside a prescription, and not an endorsement of any vendor.