What Is GIP?
Published Jul 1, 2026 · 5 minute read
GIP is the quieter of the two incretin hormones, overshadowed by its famous sibling GLP-1. But GIP sits at the center of one of the most fascinating puzzles in metabolic medicine: some drugs work by switching its receptor on, and others work by switching it off, yet both can drive weight loss.
Key Takeaways
- GIP stands for glucose-dependent insulinotropic polypeptide; it is one of the body's two main incretin hormones.
- Like GLP-1, GIP is released by the gut after eating and increases glucose-dependent insulin secretion.
- The GIP receptor is targeted by tirzepatide, a dual GIP/GLP-1 agonist.
- Intriguingly, some drugs activate (agonize) the GIP receptor while others block (antagonize) it, and both approaches show weight effects.
- GIP was historically called gastric inhibitory polypeptide before its incretin role was understood.
- This page is educational and is not medical advice.
1. What Is GIP?
GIP stands for glucose-dependent insulinotropic polypeptide. It is a hormone released by cells in the upper small intestine after eating, and it is one of the two main human incretins, the other being GLP-1.
Like GLP-1, GIP increases insulin secretion in a glucose-dependent way, meaning it acts most strongly when blood sugar is rising after a meal. That shared job is why both hormones are grouped together as incretins.
| Term | What it means |
|---|---|
| GIP | Glucose-dependent insulinotropic polypeptide, an incretin hormone. |
| Incretin | A gut hormone that raises insulin after eating. |
| GIP receptor | The cell receptor GIP binds to; targeted by several modern drugs. |
| Agonist / antagonist | A drug that activates a receptor / a drug that blocks it. |
2. A Confusing Name History
GIP was first described as gastric inhibitory polypeptide, named for an early observation that it seemed to reduce stomach acid secretion. As research advanced, scientists realized its dominant role in the body is stimulating insulin, so the meaning of the abbreviation was updated to glucose-dependent insulinotropic polypeptide. The letters stayed the same; the understanding changed.
3. GIP vs GLP-1
Both hormones are incretins, but they specialize differently.
| Feature | GIP | GLP-1 |
|---|---|---|
| Raises insulin after meals | Yes | Yes |
| Slows gastric emptying | Minimal | Strong |
| Appetite effect | Complex, still studied | Strong appetite reduction |
| Role in fat metabolism | Prominent | Present |
GLP-1’s powerful appetite and stomach-emptying effects made it the early star of weight management. GIP’s story is more nuanced, which leads directly to the field’s most surprising debate. For the broader comparison, see GLP-1 vs GLP-2 vs GLP-3.
4. The Agonist vs Antagonist Puzzle
Here is what makes GIP genuinely interesting. With most receptors, you would expect only one direction to be useful. With the GIP receptor, both activating and blocking it have shown weight effects in trials, as long as GLP-1 activity is also present.
- GIP receptor agonism (switching it on): Tirzepatide is a dual GIP/GLP-1 agonist and is FDA-approved. Investigational VK2735 and the triple agonist retatrutide also activate the GIP receptor.
- GIP receptor antagonism (switching it off): MariTide is designed to block the GIP receptor while activating the GLP-1 receptor.
Both strategies have produced weight loss in studies. Researchers are still working out the mechanism, and this remains an open scientific question.
5. Which Drugs Involve GIP
| Drug | GIP action | Status |
|---|---|---|
| Tirzepatide | GIP receptor agonist (with GLP-1) | FDA-approved |
| VK2735 | GIP receptor agonist (with GLP-1) | Investigational |
| Retatrutide | GIP receptor agonist (with GLP-1 and glucagon) | Investigational |
| MariTide | GIP receptor antagonist (with GLP-1) | Investigational |
6. Where GIP Fits
GIP is the second incretin, less famous than GLP-1 but central to the most advanced dual and triple agonist drugs. Understanding it explains why “dual agonist” is such a common phrase and why the same receptor can be a target for both activation and blockade.
- GIP = glucose-dependent insulinotropic polypeptide, an incretin hormone.
- Incretin partner = works alongside GLP-1.
- Agonized by tirzepatide, VK2735, and retatrutide.
- Antagonized by MariTide, an unusual and actively studied approach.
7. What Is GIP FAQ
What is GIP in simple terms?
GIP is a hormone released by the gut after eating that helps the pancreas release insulin when blood sugar is rising. It is one of the two main incretin hormones, the other being GLP-1.
What does GIP stand for?
GIP stands for glucose-dependent insulinotropic polypeptide. It was originally named gastric inhibitory polypeptide, but the name was updated as scientists learned its main role is stimulating insulin in a glucose-dependent way.
How is GIP different from GLP-1?
Both are incretins that raise insulin after meals. GLP-1 also slows the stomach and strongly reduces appetite. GIP has a larger role in fat metabolism, and its effect on appetite is more complex, which is part of why the GIP receptor is studied with both activating and blocking drugs.
Which drugs target GIP?
Tirzepatide (Mounjaro, Zepbound) is a dual GIP/GLP-1 receptor agonist, and several investigational drugs like VK2735 and retatrutide also activate the GIP receptor. In contrast, MariTide is designed to block the GIP receptor while activating GLP-1.
Why would a drug block GIP instead of activating it?
It is one of the most interesting puzzles in the field: both activating and blocking the GIP receptor can produce weight loss in trials when combined with GLP-1 activity. Researchers are still studying why, and this page does not take a clinical position on which approach is better.