Is GLP-3 a real hormone?

No. The body makes GLP-1 and GLP-2; there is no GLP-3. The word is informal shorthand for retatrutide.

Is “GLP-3” the same thing as retatrutide?

In practice yes — that is what people mean by it. The accurate description is “triple agonist”.

How is GLP-3 different from tirzepatide?

Tirzepatide activates two receptors, GIP and GLP-1. Retatrutide adds a third, the glucagon receptor.

Is retatrutide approved?

No. It remains investigational and is only available through clinical trials.

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 returns the syringe units. It converts your own numbers; it never suggests a dose.

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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) ↗
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) ↗
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 <797>) ↗

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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