Klotho

Klotho is a naturally occurring anti-aging protein your kidneys produce, not a small synthetic peptide like most entries on this site — the full protein is over 1,000 amino acids and roughly 130 kilodaltons. Lower blood levels of Klotho are linked to aging and kidney disease in human population studies, and injecting the protein, or a fragment of it, has improved memory and reduced markers of aging in mice and, in one 2023 study, aged monkeys. No human dosing trial exists, and it is not an approved drug or a legitimately sourced consumer product, despite substantial social media buzz.

Research snapshot

Peptide category	Longevity / anti-aging protein (not a short synthetic peptide — full protein is ~1,012 residues, ~130 kDa)
Primary research interest	Cognitive aging, kidney protection, lifespan extension
Highest available evidence	Human observational data for naturally circulating Klotho levels; the injected/therapeutic form has animal data only, including one nonhuman primate study
Human research available	No — injected/therapeutic Klotho has not been tested in humans. Human data exists only for naturally circulating blood levels (observational)
Development status	Preclinical (protein/fragment therapeutics); a separate klotho mRNA therapeutic and a separate klotho gene therapy are each in very early human trials — neither is the injectable protein discussed online
Regulatory status	Not approved anywhere as a drug or supplement
Last reviewed	September 27, 2026

Technical identity

Primary name	Klotho (alpha-Klotho / KL)
Alternative names	α-Klotho, soluble Klotho (s-Klotho), KL1 domain, KP1/KP6 (short KL1-derived research fragments)
Peptide sequence	Not applicable at the protein level — full-length transmembrane protein, not a short defined peptide sequence
Amino-acid length	Full-length ~1,012 amino acids (human); the soluble ectodomain is a large fragment of this, not a short peptide
Molecular formula	Not applicable at the protein level
Molecular weight	Full-length membrane protein ~130 kDa; the soluble form is a large glycoprotein fragment of comparable scale
CAS Registry Number	Not reliably established — Klotho is a protein product, not a single registered small molecule/peptide, and vendor “Klotho peptide” products do not correspond to one verified CAS number
PubChem CID	Not applicable at the protein level
UNII	Not established
DrugBank ID	Not established
Chemical modifications	None relevant — endogenous protein/protein fragment, not a synthetically modified peptide
Peptide class	Longevity/anti-aging protein; distinct from the short synthetic research peptides covered elsewhere on this site
Primary biological target	Co-receptor with FGF23 at the cell membrane; the shed soluble form also acts hormone-like on brain, kidney, and vasculature independent of FGF23
Developer or originator	Discovered 1997 (Kuro-o et al.); named after the Greek Fate who spins the thread of life
Development status	No approved Klotho protein or peptide therapeutic exists; separate klotho-gene and klotho-mRNA therapeutics are in very early human trials from different companies

What is Klotho?

Klotho is a protein your own body makes, mostly in the kidneys, and to a lesser degree in the brain and other tissues. It comes in two forms: a version anchored to the cell membrane, and a “soluble” version that gets cut loose and circulates in blood and spinal fluid like a hormone. Blood levels of Klotho decline with age, and lower levels are associated in human population studies with kidney disease, cardiovascular disease, and cognitive decline.

It was discovered in 1997 when a mutant mouse missing the Klotho gene showed a dramatic, premature-aging phenotype and a drastically shortened lifespan; mice engineered to have more Klotho lived longer than normal. That single finding launched nearly three decades of research into whether replacing or boosting Klotho could do the reverse in aging animals, and eventually humans.

Importantly, essentially none of that research has been done with the small “Klotho peptide” vials sold online. Most legitimate research uses either the intact soluble protein, as in the mouse and monkey studies below, or specific short fragments derived from one region of it, called KL1, engineered for a particular mechanism such as blocking a fibrosis pathway in the kidney. There is no published evidence connecting a specific commercially available vial to any of these studies.

Klotho has also become one of the more talked-about longevity compounds on social media and in online research communities over the past year, largely on the strength of the 2023 aged-monkey memory study described below. That online attention is real and worth acknowledging, but it is separate from the underlying evidence, which this page keeps clearly labeled throughout.

How does it work?

Plain-English explanation

Klotho acts like a hormone your kidneys make less of as you age. When levels are higher, tissues throughout the body, especially the brain and kidneys, seem to handle stress and aging better. Giving extra Klotho protein to old mice, and in one study old monkeys, improved memory and markers of tissue aging, at least temporarily.

Technical explanation

Membrane-bound Klotho functions as an obligate co-receptor for FGF23, regulating phosphate and vitamin D metabolism. The soluble ectodomain, released by proteolytic shedding, has broader FGF23-independent actions: it inhibits several pro-aging and pro-fibrotic signaling pathways, including insulin/IGF-1 and TGF-β signaling, and has been shown to modulate NMDA receptor subunit composition in the hippocampus, a proposed mechanism for its cognitive effects.

Potential benefits and research applications

Cognitive function in aging

Human observational studies link higher blood Klotho levels to better cognitive performance across the lifespan. In mice, a single injection of the KL1 fragment or the intact protein improved learning and memory in young, aging, and Alzheimer’s-model animals. In 2023, a single low-dose injection of the intact secreted protein improved memory in aged rhesus monkeys, with effects lasting at least two weeks. This is animal evidence only; no human trial of injected Klotho for cognition exists.

Kidney protection and anti-fibrotic effects

Short Klotho-derived fragments, KP1 and KP6, reduced fibrosis markers in mouse models of kidney injury and diabetic kidney disease. Animal evidence only.

Longevity and anti-aging

The foundational finding, that Klotho-deficient mice age rapidly and die young while Klotho-overexpressing mice live longer, is well established in mice. This has not been demonstrated with an exogenous Klotho therapeutic in any species with lifespan as the endpoint outside of genetic mouse models.

What dosage information circulates?

Figures in this section summarize amounts and schedules reported in published research or circulating online. Their inclusion documents what is reported and does not establish that a regimen is verified, safe, effective, or appropriate.

Reported use or research objective	Route reported	Amount reported	Frequency reported	Reported duration	Evidence or source category
Memory enhancement, aged nonhuman primates (Prater 2023)	Subcutaneous	10 mcg/kg (secreted protein) — notably, higher doses of 20 and 30 mcg/kg did not work in this study	Single injection	Effects observed for at least 2 weeks	Published animal research
Cognitive enhancement, mice (KL1 fragment)	Systemic injection	Not converted to a standard human-equivalent figure in source material	Single or short-course	Days to weeks	Published animal research
Anti-fibrotic effect, kidney injury (KP1/KP6 fragments)	IV bolus / chronic infusion	Not specified in human-equivalent terms	Bolus or multi-week infusion	Weeks	Published animal research
General “anti-aging” use (community/social media)	Subcutaneous (as sold)	No consistent figure identified	No consistent figure identified	No consistent figure identified	Social media / community / vendor reported — origin unclear; widely repeated online, but no original source could be traced

Amounts studied in human research

No established or reliably sourced dosing information was identified. Injectable Klotho protein or its fragments have not been tested in a registered human clinical trial. Human data exists only for naturally circulating Klotho levels, measured observationally, which did not involve dosing anyone with the protein.

Amounts studied in animal research

A single low-dose (10 mcg/kg) subcutaneous injection of secreted klotho protein improved memory in aged rhesus macaques for at least two weeks; higher doses of 20 and 30 mcg/kg did not work (Prater et al., Nature Aging, 2023; 18 monkeys, mean age approximately 22 years). Mouse studies using the KL1 fragment for cognition, and the KP1/KP6 fragments for kidney fibrosis, used systemic or IV injection at amounts that vary by study and were not converted to standard human-equivalent figures in the source material (evidence category: published animal research).

Practitioner and community-reported protocols

Vendor and social-media sources describe subcutaneous “Klotho peptide” use for general anti-aging purposes, but no consistent amount, frequency, or duration could be identified, and no original source could be traced. Widely repeated online, but its original source could not be verified. Klotho is also a good example of how a single striking animal study can generate a large amount of social media and online-community discussion well before any human evidence exists: the 2023 primate memory study in particular gets cited constantly across social platforms, wellness content, and research forums, usually stripped of the caveats above, namely a small sample, a primate rather than human study, and the finding that lower doses beat higher ones. That online buzz is a large part of why interest in Klotho has outpaced what has actually been established.

Side effects, risks, and limitations

No human safety data exists for injected Klotho protein or fragments at any dose, because no human trial has been conducted. Animal studies have not focused on establishing a human safety profile. Products sold online as “Klotho peptide” carry the same generic research-chemical concerns as any unregulated compound: unverified purity and identity, unknown actual dose per vial, and no sterility assurance, compounded here by the fact that the specific product being sold typically cannot even be matched to a specific published study.

Regulatory and developmental status

No form of Klotho protein or peptide is FDA-approved or approved by any other regulatory body, for any indication. It is not legally marketed as a supplement or research chemical with any recognized identity standard. Separately, a klotho mRNA therapeutic and an unrelated klotho gene therapy program have each begun very early-phase human testing as of 2026 from different companies; both are experimental, unapproved, and not the product form discussed elsewhere on this page. Date verified: 2026-09-21.

Frequently asked questions

What is Klotho?

A protein your kidneys naturally produce that declines with age; low blood levels are linked to worse aging-related outcomes in humans.

Is “Klotho peptide” the same thing scientists study?

Usually not exactly. Most research uses the intact protein or a specific engineered fragment (KL1, KP1, KP6), not necessarily whatever is in a commercially sold vial.

What dose has been studied?

Only in animals. The most relevant figure is 10 mcg/kg as a single subcutaneous injection in aged monkeys, and that study found higher doses did not work.

Has Klotho been studied in humans?

Only observationally, by measuring natural blood levels. No human trial of an injected Klotho product has been published.

Is it approved for anything?

No.

Why is it suddenly popular online?

The monkey and mouse cognition data is genuinely striking, and it has been widely shared and discussed across social media and online research communities, but the jump from those animal results to an unregulated vial with no matching human data is a large one.

What remains unknown?

Whether any effect seen in mice or monkeys translates to humans at all, what a human dose would even look like, and whether products sold as “Klotho peptide” contain anything resembling what was used in the actual research.

Bottom line

Klotho has some of the most genuinely interesting animal longevity and cognition data of any compound on this site, including a well-designed nonhuman primate study, real published science rather than theory. But there is a complete gap between that research and what is being sold and discussed online: no human trial exists, no verified human dose exists, and the specific studies people cite were not done with a product anyone can currently buy. A good deal of the current interest is being driven by social media and online community discussion of that one primate study, often without the caveats that come with it. This is a case where the underlying science is worth taking seriously and the commercial hype around it is worth taking with real skepticism.