Lab Reference Library / Klotho (Soluble Alpha-Klotho)
Longevity & Aging
Klotho (Soluble Alpha-Klotho)
sKL · Soluble Klotho · Alpha-KlothoReference range, optimal functional medicine levels, and why klotho is the most compelling longevity protein identified, why it declines progressively with age, and why higher klotho levels are associated with longer lifespan, better cognitive function, improved cardiovascular health, and superior kidney function.
Longevity MarkerMost Searched
Standard Range327 to 1,187 pg/mL
FM OptimalAbove 700 pg/mL
Age-Related DeclineYes
Unitspg/mL
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Category: Longevity & Aging | Also known as: sKL, Soluble Alpha-Klotho, Soluble Klotho, FGF23 Co-Receptor
1. What This Test Measures
Soluble alpha-klotho (sKL) is the circulating form of klotho, produced when the extracellular domain of transmembrane klotho is cleaved by proteases (ADAM10 and ADAM17) and released into the bloodstream, urine, and CSF. Klotho is expressed primarily in the kidney distal tubule, choroid plexus, and parathyroid gland. As a co-receptor for FGF23, membrane-bound klotho regulates phosphate and vitamin D metabolism. Soluble klotho exerts pleiotropic anti-aging effects independently, inhibiting pro-aging signaling pathways (IGF-1/insulin, Wnt, and TGF-beta), suppressing oxidative stress, promoting endothelial function, protecting against inflammation and cellular senescence.
Klotho was named after one of the three Fates in Greek mythology who spins the thread of life. Animals overexpressing klotho live 20 to 30% longer and are protected from age-related diseases; klotho-deficient animals develop accelerated aging syndromes within weeks of birth, including premature cardiovascular disease, osteoporosis, sarcopenia, emphysema, and neurodegeneration. In humans, higher serum klotho is consistently associated with longer telomere length, lower all-cause mortality, better cognitive function, and slower kidney function decline.
2. Optimal Range and Age-Related Decline
| Soluble Klotho | Interpretation |
|---|---|
| Below 327 pg/mL | Very low: significantly below age-adjusted range; aggressive intervention warranted |
| 327 to 500 pg/mL | Low: below population median for most adult age groups; optimize klotho-raising interventions |
| 500 to 700 pg/mL | Borderline to low-normal: room for improvement; target interventions |
| Above 700 pg/mL | Optimal: above population median for most adults; associated with lower mortality |
| Above 1,000 pg/mL | Excellent: highest longevity-associated range; typical of highly fit younger adults |
Klotho declines approximately 50% between ages 20 and 70 in the general population. Age-adjusted interpretation is important: a 65-year-old with klotho of 750 pg/mL is performing well above age-matched peers, while the same value in a 25-year-old is below their expected range. Compare to age-matched population data when interpreting individual results.
3. Klotho's Anti-Aging Mechanisms
- IGF-1/insulin signaling inhibition: klotho inhibits the IGF-1 receptor and downstream PI3K/Akt signaling; reduced IGF-1 signaling is one of the most conserved longevity mechanisms across species; klotho functions analogously to IGF-1 pathway mutations that extend lifespan in model organisms
- Wnt signaling inhibition: Wnt pathway activation promotes tissue fibrosis and cancer; klotho inhibits Wnt signaling, protecting against fibrotic kidney disease, liver fibrosis, and Wnt-driven cancers
- TGF-beta signaling inhibition: TGF-beta promotes cellular senescence and fibrosis; klotho's TGF-beta inhibition protects kidneys, lungs, and cardiovascular tissue from progressive fibrotic injury
- Antioxidant upregulation: klotho upregulates FOXO transcription factors which increase antioxidant enzyme expression (SOD, catalase, peroxiredoxin); reduces oxidative stress in vascular and renal tissue
- Endothelial protection: klotho preserves endothelial nitric oxide synthase function, promotes vasodilation, and reduces endothelial senescence and apoptosis; lower klotho is associated with endothelial dysfunction and vascular calcification
- Neuroprotection: klotho reduces neuroinflammation, promotes synaptic plasticity, and protects against cognitive decline; higher CSF klotho correlates with better cognitive function in aging
4. How to Increase Klotho
Evidence-Based Strategies
- Aerobic exercise: one of the most consistently demonstrated klotho-raising interventions; even moderate exercise (30 minutes, 5 days weekly) increases serum klotho by 10 to 20%; high-intensity interval training (HIIT) may produce larger klotho responses; exercise also preserves kidney function, the primary klotho-producing organ
- Vitamin D3 optimization to 60 to 80 ng/mL: the vitamin D receptor (VDR) directly upregulates klotho gene transcription; vitamin D deficiency is one of the most actionable and common causes of reduced klotho; every 10 ng/mL increase in vitamin D is associated with meaningful klotho improvement
- Caloric restriction and intermittent fasting: reduce IGF-1 and insulin signaling that suppresses klotho; fasting-induced AMPK activation upregulates klotho expression
- Mediterranean diet: associated with higher klotho levels in multiple observational studies; the polyphenol, omega-3, and anti-inflammatory components contribute to klotho preservation
Nutritional Support
- Reduce dietary phosphate: high phosphate intake suppresses klotho production; processed foods (which extensively use phosphate additives for preservation and texture) and phosphoric acid in sodas are the primary high-phosphate sources in the Western diet; natural whole food phosphate does not have the same suppressive effect
- Magnesium optimization: magnesium is required for hundreds of enzymatic reactions; deficiency impairs vitamin D activation and the downstream klotho-promoting effects of vitamin D receptor signaling
- Omega-3 fatty acids: reduce systemic inflammation and oxidative stress that suppress klotho production; the anti-inflammatory effect on the kidney tubule is particularly relevant for klotho preservation
- Resveratrol and polyphenols: activate SIRT1, which upregulates klotho expression through epigenetic mechanisms; quercetin, pterostilbene, and other polyphenols have klotho-supporting evidence in animal models
Kidney Protection
- Protect kidney function above all else: the kidney is the primary klotho-producing organ; any cause of CKD dramatically reduces klotho; kidney-protective strategies are simultaneously klotho-protective strategies
- Control blood pressure rigorously: hypertension is the most common cause of CKD in the US; blood pressure above 130/80 accelerates kidney function decline and klotho reduction
- Optimize blood glucose and HbA1c below 5.7%: diabetic nephropathy is the most common cause of ESRD and is a major klotho-depleting condition
- Avoid nephrotoxic medications and substances: NSAIDs, contrast dye, aminoglycosides, and heavy metals all reduce kidney function and klotho production
- SGLT2 inhibitors (empagliflozin, dapagliflozin) and ACE inhibitors: independently protective of kidney function and may directly increase klotho production in the kidney tubule through separate mechanisms
5. Related Lab Tests
GDF-15Longevity Companion Marker; Both Reflect Aging Biology
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Vitamin DVitamin D Directly Upregulates Klotho Gene Expression
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eGFRKidney Function is Primary Klotho Production Determinant
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RBC MagnesiumRequired for Vitamin D Activation and Klotho Support
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Telomere LengthHigher Klotho Correlates with Longer Telomeres
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IGF-1Klotho Inhibits IGF-1 Signaling; Longevity Pathway
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6. Clinical Perspective
Clinical Perspective
Klotho is the longevity marker that most compellingly reframes the conversation about aging as something biological and partially modifiable rather than inevitable and fixed. When I measure klotho in a 58-year-old with CKD stage 2 and find it at 340 pg/mL, decades below where it should be for their age, I can directly connect that to their cardiovascular calcification risk, their cognitive decline trajectory, and their accelerating fibrosis risk in multiple organs. And then I can point to the intervention: protect the kidneys at all costs, optimize vitamin D, get daily exercise, eliminate phosphate-additive processed foods, and watch the klotho trend over the next 12 months. I have had patients raise klotho meaningfully with these interventions. That is anti-aging medicine with measurable biological feedback.
Brian Lamkin, DO | Founder, The Lamkin Clinic | Edmond, Oklahoma
7. Frequently Asked Questions
What is klotho and why is it important for longevity?
Klotho is a hormone produced primarily by the kidneys that functions as a powerful anti-aging factor. Animals overexpressing klotho live 20 to 30% longer; klotho-deficient animals develop accelerated aging syndromes. In humans, higher serum klotho is associated with lower all-cause mortality, better cognitive function, lower cardiovascular disease risk, and slower kidney function decline. Klotho inhibits pro-aging IGF-1, Wnt, and TGF-beta signaling while promoting antioxidant defenses and endothelial function.
How do you increase klotho levels?
Evidence-based strategies: aerobic exercise (10 to 20% increase with regular activity), vitamin D3 optimization to 60 to 80 ng/mL (VDR directly upregulates klotho gene transcription), reducing dietary phosphate additives from processed foods, magnesium optimization, omega-3 fatty acids, caloric restriction and intermittent fasting, Mediterranean diet, and kidney protection through blood pressure control, blood glucose optimization, and avoiding nephrotoxic substances.
What is the relationship between klotho and kidney disease?
The kidneys are the primary producers of circulating klotho. As kidney function declines in CKD, klotho production falls proportionally, creating a progressive klotho deficiency that accelerates cardiovascular, metabolic, and skeletal complications of CKD. This creates a vicious cycle: CKD causes low klotho, and low klotho accelerates CKD progression. Kidney protection is therefore simultaneously the most impactful klotho-preservation strategy available.
What causes klotho to decline?
Klotho declines approximately 50% between ages 20 and 70. Additional accelerators include: chronic kidney disease (major), vitamin D deficiency (actionable), chronic inflammation, oxidative stress, sedentary lifestyle, sleep deprivation, high dietary phosphate from processed foods and sodas, and certain medications including proton pump inhibitors.
Content authored and clinically reviewed by Brian Lamkin, DO, founder of The Lamkin Clinic in Edmond, Oklahoma. Brian Lamkin, DO has 25+ years of experience in functional and regenerative medicine. This page reflects current functional medicine practice standards and is updated as new clinical evidence becomes available.
Klotho is the longevity hormone that most directly connects kidney function to cardiovascular calcification, cognitive aging, and biological lifespan.
Klotho is the most compelling anti-aging biomarker identified. Schedule a consultation for a complete longevity panel including klotho, GDF-15, NAD+, and telomere length.
Schedule a ConsultationMedical Disclaimer: This content is provided for educational purposes only and is not intended as a substitute for professional medical advice, diagnosis, or treatment. Lab interpretation should always be performed in clinical context by a qualified healthcare provider. Reference ranges and optimal targets may vary based on individual patient history, clinical presentation, and laboratory methodology. Schedule a consultation to discuss your specific results with Dr. Lamkin.