A free, self-service longevity toolkit
Precision health shouldn't be only for the top 1%. So I team up with the researchers behind the best published models and turn their work into free tools for interpreting lab results.
- Best science, straight from the source
- Used by labs and clinics
Interpret Blood Test Results
100% free and private. Instant results, no email required.
Zsolt Szabo Founder, Longevity-tools.com
Precision health consultant for longevity clinics
Humanity's Bortz Blood Age
Biological age from a routine blood test. Dr. Joshi co-authored the best-performing model built on standard lab tests. Methylation clocks can return different ages for the same blood sample, while these markers are reliable and also show how each organ system is doing.
Iron Status Interpreter
77% of young women are iron deficient, and most never find out. Standard ranges reflect what is common, not what is healthy, and inflammation can make ferritin look OK. Together with Dr. Skikne, I built a tool that accounts for both.
Conquer Aging Or Die Trying!
The inspiration behind Longevity-tools. Michael is a longevity researcher and arguably today's most rigorous biohacker. Many of the optimal ranges used here come from his work.
Precision Health Tools
Calculators and interpreters to help you optimize your health
Bio-age calculators
Resources
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GLP-1 Pen Click Calculator
Convert a target dose into clicks and view complete dose charts for common Ozempic, Wegovy, Mounjaro, and Zepbound pens.
Recommended Lab Tests for Longevity
Most impactful blood tests for optimal health.
How to Prepare for a Blood Test
What to do days before a blood draw to get the most accurate and comparable results.
Interpreters
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B12 Status Interpreter
Combines vitamin B12 related markers into the cB12 indicator, estimates body B12 stores, and provides a personalized supplementation plan.
CVD Risk Interpreter - PREVENT
Estimates cardiovascular risk from routine labs, explains the results and proposes personalized prevention strategies.
Kidney Health Interpreter
Comprehensive kidney function assessment combining blood and urine markers to visually interpret, stage and differentiate kidney dysfunction, while providing personalized risk predictions.
Thyroid Function Interpreter
Comprehensive assessment of thyroid function blood tests with HPT axis visualizations designed to detect thyroid-related dysfunction early.
Male Hormones Interpreter
Comprehensive male hormone interpretation that visualizes the testosterone production and feedback pathway to identify the true root cause of hormonal imbalances.
Glucose Metabolism Interpreter
Provides a comprehensive metabolic assessment of blood glucose control using a static multi-biomarker approach.
Liver Function Blood Test Interpreter
Comprehensive liver function test interpretation tool that automatically calculates key liver health indexes and provides recommendations based on official clinical guidelines.
Iron Status Interpreter
Calculates Body Iron Stores and provides a personalized intervention plan.
Grip Strength Interpreter
Discover your grip strength percentile, evaluate its impact on mortality, and estimate the risk of future muscle weakness.
coming soon
Body Weight Interpreter
Analyzes body weight using multiple indexes, evaluates its impact on longevity, and calculates the optimal weight. Provides evidence-based nutrition and weight-loss recommendations.
coming later
Blood Pressure Interpreter
Guided protocols for measuring blood pressure in various positions and comprehensive analysis of results.
Have an idea for a new tool? .
Optimal Biomarker Ranges
Lab reference ranges for optimal health
Liver and Gallbladder
Blood Health
Vital Signs
Immunity
Tumor
The "normal" range on your lab result indicates .
Calculated Indexes
Standalone calculators that complement my full interpretation tools
ANI
ALD/NAFLD Index is used for distinguishing Alcoholic from Nonalcoholic Fatty Liver Disease.
C-peptide/insulin
C-peptide to insulin molar ratio is helpful in detecting exogenous insulin use, impaired hepatic insulin clearance and impaired C-peptide clearance by the kidneys.
D/T Bilirubin Ratio
The D/T ratio is used to differentiate between different types of jaundice and liver injury patterns.
eGFRcr
Estimated glomerular filtration rate from serum creatinine using the race-free CKD-EPI 2021 equation. Affected by muscle mass, meat or creatine intake, exercise, sarcopenia, and immobility.
eGFRcr-cys
Combined creatinine and cystatin C estimate of glomerular filtration correlates best with the measured GFR.
eGFRcys
Estimated glomerular filtration rate from cystatin C. Independent of muscle mass. Affected by thyroid function, chronic inflammation, corticosteroids, and obesity.
eGFRdiff
eGFRdiff is calculated by subtracting creatinine eGFR (eGFRcr) from cystatin C eGFR (eGFRcys). It helps show whether the two kidney estimates agree and, if they do not, what the disagreement may mean.
FIB-3
The Fibrosis-3 Index is an improved version of the FIB-4, that does not include age. It outperforms both FIB-4 and APRI.
FLI
Fatty Liver Index is one of the best models to predict liver fat content.
FT3/FT4 molar ratio
A crude proxy for peripheral T4-to-T3 conversion (deiodinase activity).
fT3/rT3 ratio
Free T3 to reverse T3 ratio reflects the balance between thyroid hormone activation (T4→T3) and inactivation (T4→rT3).
HOMA-IR
HOMA1-IR has a poor correlation (r = -0.60) with the gold standard - Glucose clamp index of insulin sensitivity.
LSS
Liver stiffness score is currently one of the best models to predict liver fibrosis. Outperforms FIB-4, APRI and HSI. Trained on NHANES dataset.
PTFQI
Estimated pituitary TSH sensitivity to free T4, maintaining stability at extreme hormone values.
PTFQI-FT3
Estimated pituitary TSH sensitivity to free T3. This is a newer, less validated index, but may add value in some contexts.
QUICKI
QUICKI correlates well (r = 0.78) with the gold standard - Glucose clamp index of insulin sensitivity
R-Factor
R-Factor is used for distinguishing acute liver injury (Hepatocellular from Cholestatic). Often used when drug induced liver injury (DILI) is suspected.
Risk-weighted ApoB
Risk-weighted ApoB is currently the best single marker of atherogenic risk that accounts for the differing cardiovascular risk contributions of LDL, TRL/remnant, and Lp(a) particles.
SPINA-GD
Estimated maximum peripheral T4 to T3 conversion. Unlike simple FT3/FT4 ratios, it accounts for nonlinear enzyme kinetics.
SPINA-GT
Estimated maximum thyroid hormone production capacity of the gland under TSH stimulation. Not sensitive to isolated secondary (pituitary) disorders.
Triglyceride/HDL
Triglyceride-to-HDL ratio is a surrogate marker of insulin resistance, NAFLD and atherogenic dyslipidemia.
TSHI
Quantifies pituitary TSH sensitivity to free T4. Commonly used, but less reliable at extreme hormone values.
TT/E2
Ratio of total testosterone to estradiol. Used as a rough proxy for aromatase activity / relative estrogen dominance in men.
TyG
Triglyceride-glucose index is an inexpensive non-insulin surrogate marker of insulin resistance.
TyG-BMI
Triglyceride-Glucose index multiplied by BMI is one of the best models to predict NAFLD.
uACR
Urine Albumin-to-Creatinine Ratio from a spot urine sample. Used to detect and stage albuminuria, an early marker of kidney damage and a strong predictor of cardiovascular and renal outcomes.
uPCR
Urine Protein-to-Creatinine Ratio from a spot urine sample. Used to detect and stage proteinuria; captures albumin and other proteins, complementing uACR when non-albumin proteinuria is suspected.
Please send me relevant research and feedback.
Any feedback is welcome at .
I am particularly interested in research on biomarkers associated with all-cause mortality and on defining optimal reference ranges.