What Is an Incretin?
Published Jul 1, 2026 · 6 minute read
An incretin is a hormone your gut releases after a meal that tells the pancreas to make more insulin. Two of them, GLP-1 and GIP, sit at the center of nearly every modern weight and diabetes medicine in the news. Understanding incretins makes the whole drug landscape click into place.
Key Takeaways
- An incretin is a gut hormone released after eating that increases insulin secretion in a glucose-dependent way.
- The two main human incretins are GLP-1 and GIP.
- The incretin effect describes why an oral glucose load triggers more insulin than the same amount of glucose given intravenously.
- Most modern GLP-1 weight and diabetes medicines are incretin-based therapies that mimic or amplify these hormones.
- Glucagon and amylin are related metabolic hormones but are not incretins.
- This page is educational and is not medical advice.
1. What Is an Incretin?
An incretin is a hormone secreted by the gut in response to food, especially carbohydrates, that increases the release of insulin from the pancreas. The key feature is that incretins boost insulin in a glucose-dependent way: they have the strongest effect when blood sugar is rising after a meal, and much less effect when blood sugar is already low.
The two main human incretins are GLP-1 (glucagon-like peptide-1) and GIP (glucose-dependent insulinotropic polypeptide). If you have read about what a GLP-1 is, you have already met one half of the incretin system.
| Term | What it means |
|---|---|
| Incretin | A gut hormone that raises insulin after eating. |
| GLP-1 | One of the two main incretins; also curbs appetite and slows the stomach. |
| GIP | The other main incretin. |
| Incretin effect | Why eating glucose triggers more insulin than injecting it. |
2. The Incretin Effect
The reason scientists know incretins exist comes from a simple experiment. If you give someone glucose by mouth, their insulin response is much larger than if you give them the exact same amount of glucose directly into a vein. That gap is called the incretin effect, and it exists because eating triggers gut hormones that the intravenous route bypasses.
In healthy people, the incretin effect can account for a large share of the insulin released after a meal. In type 2 diabetes, the incretin effect is blunted, which is part of why incretin-based medicines became such an active area of research.
Illustrative only: oral glucose triggers a larger insulin response than the same glucose given by vein. That gap, the highlighted segment, is the incretin effect.
3. GLP-1 vs GIP: The Two Incretins
Both GLP-1 and GIP are released by specialized cells in the gut lining after eating, and both raise insulin. They differ in their other jobs.
| Hormone | Raises insulin? | Other notable effects |
|---|---|---|
| GLP-1 | Yes | Slows gastric emptying; reduces appetite; suppresses glucagon. |
| GIP | Yes | Roles in fat metabolism; effects on appetite still being studied. |
GLP-1’s appetite and stomach-emptying effects are a big reason the GLP-1 pathway became central to weight management, not just blood-sugar control. For the receptor-language side of this, see GLP-1 vs GLP-2 vs GLP-3.
4. Incretins vs Incretin-Based Medicines
This is the distinction that trips people up. The hormones GLP-1 and GIP are incretins. The medicines people take are not incretins themselves; they are incretin-based therapies that imitate or amplify those hormones, usually by activating the same receptors and resisting the rapid breakdown that natural incretins undergo.
- A natural incretin is a hormone your body makes.
- An incretin mimetic or receptor agonist is a drug designed to act like it.
- “Incretin-based therapy” is the umbrella term for these medicines.
5. How the Drug Classes Map to the Incretins
Once you know the incretins, the alphabet soup of modern molecules becomes a simple grid based on which receptors each one targets.
| Drug type | Receptors targeted | Examples |
|---|---|---|
| GLP-1 receptor agonist | GLP-1 | Semaglutide |
| Dual GIP/GLP-1 agonist | GIP + GLP-1 | Tirzepatide, VK2735 |
| GLP-1/glucagon agonist | GLP-1 + glucagon | Survodutide, Pemvidutide |
| Triple agonist | GIP + GLP-1 + glucagon | Retatrutide |
Note that the GLP-1/glucagon and triple agonists add a glucagon target. Glucagon is a related metabolic hormone but is not an incretin, which is why those drugs are described as incretin-based plus a glucagon component.
6. What Is Not an Incretin
Two hormones come up constantly in this space but are not incretins:
- Glucagon: a pancreatic hormone that raises blood sugar and, via its receptor, increases energy expenditure and liver fat oxidation. Targeted by drugs like survodutide and efinopegdutide, but not an incretin.
- Amylin: a hormone co-released with insulin that promotes fullness. Targeted by drugs like cagrilintide, eloralintide, and petrelintide. See What Is Amylin?.
7. Why This Matters
Understanding incretins turns a confusing list of brand names and code names into a small set of mechanisms. Almost every weight or diabetes molecule making headlines is built on the incretin system, either copying one incretin, combining two, or adding a non-incretin hormone like glucagon or amylin on top.
- Incretin = a gut hormone (GLP-1 or GIP) that raises insulin after eating.
- Incretin effect = why oral glucose beats IV glucose at triggering insulin.
- Incretin-based therapy = medicines that mimic or amplify these hormones.
- Glucagon and amylin = related hormones that are not incretins.
8. What Is an Incretin FAQ
What is an incretin in simple terms?
An incretin is a hormone your gut releases after you eat that tells the pancreas to release more insulin. Because it acts mainly when blood sugar is rising, it helps the body handle a meal. The two main human incretins are GLP-1 and GIP.
What is the incretin effect?
The incretin effect is the observation that glucose taken by mouth triggers a much larger insulin response than the same amount of glucose given by vein. The difference is caused by incretin hormones released from the gut during digestion.
Are GLP-1 drugs incretins?
GLP-1 receptor agonist medications are not incretins themselves; they are incretin-based therapies that mimic the natural incretin hormone GLP-1 by activating the same receptor. The term incretin refers to the body's own hormones.
Is glucagon an incretin?
No. Glucagon is a related pancreatic hormone, and some newer drugs target the glucagon receptor alongside GLP-1, but glucagon is not classified as an incretin. The recognized human incretins are GLP-1 and GIP.
What is the difference between GLP-1 and GIP?
Both are incretins released by the gut after eating. GLP-1 also slows gastric emptying and reduces appetite, which is central to weight-related effects. GIP is the other major incretin, and some drugs target both receptors at once.