# What is GLP-3? There is no such hormone — here's what people mean

> “GLP-3” is not a real hormone. It is internet shorthand for retatrutide, a triple agonist that activates the GIP, GLP-1 and glucagon receptors.

Source: https://glp-1-app.com/learn/what-is-glp-3/

Education · not medical advice

## What is “GLP-3”?

Short answer: there is no hormone called GLP-3. When people write “GLP-3” they almost always mean retatrutide.

### There is no GLP-3

Your body makes **GLP-1** (glucagon-like peptide-1) and **GLP-2** — two related hormones cut from the same proglucagon precursor. There is no GLP-3. The term appears in no pharmacology textbook, in no manufacturer filing, and in no regulator document.

### What people mean: retatrutide

“GLP-3” is shorthand for **retatrutide**: one molecule that switches on _three_ receptors at once — GIP, GLP-1 and glucagon. The accurate name for that is a **triple agonist**.

### Where the nickname came from

It is a generation count, not a hormone name. Each new molecule in this class added a receptor, so “GLP-3” became shorthand for “the three-receptor one”. Some sellers number their catalogue the same way.

_What the nicknames actually refer to_

| Nickname | Actual molecule | Receptors it activates | Regulatory status |
| --- | --- | --- | --- |
| “GLP-1” | Semaglutide | GLP-1 | Approved |
| “GLP-2” | Tirzepatide | GIP + GLP-1 | Approved |
| “GLP-3” | Retatrutide | GIP + GLP-1 + glucagon | Investigational |

Note the collision: **GLP-2 is a real hormone** — it comes from the same precursor as GLP-1 and helps maintain the gut lining. It has nothing to do with tirzepatide. The vendor habit of numbering products “GLP-1, GLP-2, GLP-3” borrows a real hormone name for a marketing tier.

### Retatrutide is investigational

Retatrutide is in clinical trials. It is not approved by the FDA, the EMA or any other regulator, for any use. Anything sold as “GLP-3” outside a trial is not a licensed medicine.

### If you are reconstituting a vial labelled “GLP-3”

The arithmetic does not care what the vial is called. Enter the vial strength in mg, the bacteriostatic water you added in mL, and your dose — the [retatrutide calculator](https://glp-1-app.com/calculator/retatrutide/) returns the syringe units. It converts your own numbers; it never suggests a dose.

### Keep reading

### Sources

This tool converts the numbers you enter — it never recommends a dose. Its constants are cited below; the warnings are arithmetic checks, not clinical limits.

- Syringe "units" are a volume marking, not a drug amount: a U-100 syringe reads 100 units = 1 mL (U-40 = 40 units/mL). The calculator converts mg ↔ mL ↔ units on this standard — it never assumes units equal mg.[Standard insulin concentration, U-100 = 100 units/mL (PMC5505430) ↗](https://pmc.ncbi.nlm.nih.gov/articles/PMC5505430/)
- The volume to draw is (drug ordered ÷ drug available) × the vial's total mL — i.e. dose ÷ concentration, where concentration (mg/mL) = vial mg ÷ bacteriostatic water mL. You enter every number; the tool only does this arithmetic.[Dose-volume formula — StatPearls "Dose Calculation" (Bookshelf NBK430836) ↗](https://www.ncbi.nlm.nih.gov/books/NBK430836/)
- An opened (punctured) multi-dose vial is dated and discarded within 28 days unless the manufacturer states otherwise.[CDC Injection Safety (per USP General Chapter ) ↗](https://www.cdc.gov/injection-safety/hcp/clinical-safety/index.html)

Educational content only — not medical advice, and never a recommendation about your medication or dose. Talk to your provider or pharmacist about anything that applies to you.

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