Tetrapeptide-21_Dosage, benefits & legal status
Also known as GEKG, Gly-Glu-Lys-Gly, TEGO Pep 4-17
A topical peptide for firmer, plumper skin.
Common vial size is what vendors typically sell, not a recommendation. Enter your own vial in the calculator.
What is Tetrapeptide-21?
Plain language first. The technical label stays, but it never stands alone.Overview
Used topically, it helps skin look firmer and plumper.
Tetrapeptide-21 is a cosmetic peptide that boosts skin's production of collagen and hyaluronic acid.
What it's used for
A topical peptide that tells skin to make more collagen and moisture for firmer, plumper skin.
How does Tetrapeptide-21 work?
What it does in the body, and where.Tetrapeptide-21 is a four-amino-acid cosmetic peptide aimed at both collagen and hyaluronic acid.
- 01It signals production of collagen and hyaluronic acidFirmness from one, water retention and plumpness from the other.
- 02Concentrations come from formulation practiceThere is no dose-ranging trial behind the percentages used; they are what manufacturers have settled on.
Where this compound is thought to act.
What else is it used for?
Each use below carries its own evidence level. Approved means regulators have cleared it for that purpose. Investigational means it is in trials. Early research means it is being studied and is not established.
- Firmer, plumper skin, applied to the skinOTC / supplement
- Boosting collagen and hyaluronic acidEarly research
The published record
4
Records indexed for Tetrapeptide-21
2 in humans, 2 of them original studies.
Counted from Europe PMC indexing, not read by a person. Human means indexed under humans, which includes reviews and work on human cells. Original studies exclude reviews and lab work on human cells.Last updated 12 September 2026.
At a glance
Four things to know about Tetrapeptide-21
Evidence
OTC / supplement
Category
Skin and cosmetic
Common vial
Varies
Half-life
Not measured, and not the right question
How much, and do you cycle it?
The range, and whether you take breaks.Serum, per product, daily. Not cycledCommunity practice
Used daily as part of a routine. The effect depends on continued use and returns to baseline when you stop, so there is nothing to cycle off.
How long does it stay in the body?
The half-life, and where the figure comes from.Not measured, and not the right questionNo figure
This is a topical cosmetic ingredient. A blood half-life measures how fast something leaves the bloodstream, and these are not intended to reach it in meaningful amounts. What matters for a topical is how much penetrates the skin and how long it stays in the tissue, which is a different measurement and one that is rarely published.
You can compare this against the whole library to see where it sits.
What does it cost?
Typical dose and cost, in plain numbers.Tetrapeptide-21 is not injected
It is taken on the skin (topical). Applied as a topical product at the concentration the manufacturer sets. There is no injected dose.
How do you store it?
Before mixing, and after.Room temperature, out of light. Cap it tight after each use.
Tetrapeptide-21 ships as a cream, gel, or serum. Keep it at room temperature away from sun and heat unless the label says otherwise. Refrigerating an emulsion can split the texture. Watch for color, smell, or separation changes and stop using it if any appear.
What are the side effects and cautions?
Known cautions and warnings for this compound.Who should avoid it
- A known allergy to this ingredient or to others in the same product
- Broken, cracked, or actively irritated skin
- Anyone who wants established safety data, because none exists for this compound in humans
Stop and get help
- A rash that spreads beyond where you applied it
- Swelling of the face, lips, or eyelids, or any trouble breathing
- Burning that does not settle after rinsing it off
- Anything unusual, since there is no known safety profile to compare it against
Common effects
- Very safe on the skin.
- Beyond the above, unknown. There is no reliable human data on what this compound commonly causes
Where this page says nothing is established, that means nobody has studied it, not that a compound is safe.
Is Tetrapeptide-21 approved?
And where the numbers on this page come from.Not as a medicine. Tetrapeptide-21 is sold without a prescription as a supplement or cosmetic ingredient, which is a different thing from being approved as a drug.
- Approval statusOTC / supplement
- RouteOn the skin (topical)
- CheckedAugust 2026
What has happened recently
We have not yet written a full regulatory note for this compound. The status above is current as of the date shown.
You can compare this against the whole library, or read how to check a seller.
- DoseFrom product labeling and published use.
- Vial sizeFrom what vendors typically list; not a recommendation.
- Sources
- Reviewed14 August 2026
What else is like Tetrapeptide-21?
Others in Skin and cosmetic, side by side.If you're weighing Tetrapeptide-21, it's worth reading PTD-DBM, AHK-Cu, and Acetyl Tetrapeptide-3 in the same class.
A topical peptide for firmer, plumper skin.
- Dose
- Serum, per product
- How often
- Daily
A hair-regrowth peptide from a single Korean lab, tested only in mice.
- Dose
- Topical, per product
- How often
- Daily
GHK-Cu's less-studied cousin, sold mainly for hair.
- Dose
- Topical serum, per product
- How often
- Daily
A hair peptide sold for thinning, with evidence that mostly belongs to a combination product.
- Dose
- Serum or scalp treatment, 0.1 to 5%
- How often
- Daily
Guides for this compound
- How to Reconstitute a Peptide
Mix peptide powder with bacteriostatic water, step by step.
- mcg vs mg: The Peptide Dosing Mistake to Avoid
Your vial says mg and your protocol says mcg. Here is the conversion and how to check it.
- How to Read a Peptide COA
What the purity number does and does not tell you, and how to spot an edited report.
- How to Vet a Peptide Vendor
Independent COAs, HPLC purity, and the red flags that mean walk away.
Sources
- Pintea et al., Peptides: Emerging Candidates for the Prevention and Treatment of Skin Senescence: A Review (Biomolecules 15:88)(2025)Tetrapeptide-21 is Gly-Glu-Lys-Gly, one of the smallest cosmetic peptides in use at 389 daltons, which matters because the review identifies poor skin permeability as the central problem for this whole class and puts the threshold for reasonable penetration at around 500 daltons. The claimed action is stimulation of collagen at both the messenger RNA and protein level, plus effects on hyaluronan and fibronectin. As with several others here, that sits in the review's summary table rather than in a section discussing trials.
Last reviewed 14 August 2026
Beyond these, 4 records are indexed. Browse the records