What GLP-1 actually is
GLP-1, short for glucagon-like peptide-1, is a hormone your gut releases after you eat. It tells your pancreas to release insulin, slows how fast food leaves your stomach, and signals your brain that you’re full. Drugs in this class copy that hormone’s effect, lasting far longer than the natural version, which breaks down within minutes.
Retatrutide and tirzepatide go further. Tirzepatide also activates the GIP receptor, and retatrutide activates GIP and glucagon receptors on top of GLP-1. Each is a peptide, a chain of amino acids, which is exactly why they’re fragile compared with a small-molecule tablet.
Why the peptide structure matters here
A peptide’s chain can break down through a chemical process called degradation, which speeds up in heat and slows down in the cold. That single fact is the reason cold-chain shipping and proper storage exist at all for these drugs.
From lab to injection
A vial goes through several temperature transitions before it’s ever used: manufacturing and testing, shipping to a supplier, storage at the supplier, shipping to a buyer, and storage at home. Each step is a chance for the cold chain to break if it isn’t handled correctly.
Why this differs from a typical tablet
A tablet is chemically stable at room temperature for years. A peptide vial, whether still lyophilised (freeze-dried powder) or already reconstituted into liquid, has a much narrower window of stability, which is why storage and shipping guidance for these products looks so different from what you’d expect for ordinary medication.
The takeaway
Understanding how these drugs work also means understanding why they need careful handling. The chemistry that makes them effective is the same chemistry that makes them sensitive to heat.