What is GLP-1? The hormone, what it stands for, and how it works

What are GLP-1 receptor agonists?

GLP-1 stands for "glucagon-like peptide-1," a hormone produced in the intestines after a meal. A GLP-1 receptor agonist is a medicine engineered to bind to the same receptors that this natural hormone uses. Because the body breaks down natural GLP-1 within a minute or two, these medicines are designed to stay active far longer, so a single dose can work over many hours or days.

How do they work in the body?

GLP-1 receptor agonists act in several places at once. The most commonly described effects are:

• Insulin signaling: they prompt the pancreas to release insulin when blood sugar is high.
• Glucagon: they reduce glucagon, a hormone that tells the liver to release sugar.
• Gastric emptying: they slow how quickly the stomach empties, so food stays longer and you feel full longer.
• Appetite: they act on appetite centers in the brain, which can reduce hunger signals.

These are descriptions of how the medicine class is understood to act. How strongly and how quickly any of this happens varies from person to person, and these medicines are only prescribed and supervised by a doctor.

The common medicines

Several GLP-1 medicines are on the market. They share a similar mechanism but differ in their active ingredient and how they are used. Common brand names include Ozempic®, Wegovy®, Mounjaro®, Zepbound®, Saxenda®, Victoza®, and Trulicity®.

• Semaglutide — the active ingredient in Ozempic® and Wegovy®.
• Tirzepatide — the active ingredient in Mounjaro® and Zepbound®. It binds both the GLP-1 and the GIP receptor, which is why it is described as a "dual agonist."
• Liraglutide — the active ingredient in Saxenda® and Victoza®.
• Dulaglutide — the active ingredient in Trulicity®.

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Injection versus oral forms

Most GLP-1 medicines are given as a subcutaneous injection: a small injection into the fatty tissue just under the skin, often in the abdomen, thigh, or upper arm. Some are taken weekly and others daily, depending on the medicine. There are also oral (tablet) versions of certain GLP-1 medicines. The exact form, schedule, and technique are set by your prescription, and the package instructions and your healthcare provider explain how to use a given product.

How long they stay in the body

A medicine's "half-life" is roughly the time it takes for half of a dose to leave the body. This is one reason different GLP-1 medicines are dosed daily or weekly. Approximate half-lives reported for these active ingredients are:

• Semaglutide: about 7 days (typically dosed weekly).
• Tirzepatide: about 5 days (typically dosed weekly).
• Dulaglutide: about 5 days (typically dosed weekly).
• Liraglutide: about 13 hours (typically dosed daily).

These figures are general reference values; the actual numbers for a specific product appear in its official labeling, and your prescription dictates how and when you take it.