Measurement · aging
Biological age tests: what they measure and which are worth paying for
A biological age test can return results up to 9 years apart on the same DNA sample (per Higgins-Chen, Nature Aging 2022), while a free floor test has published mortality data. Start free, then decide whether a kit is worth the money.
On this page
The short version
What is a biological age test?
A biological age test estimates how old your body appears to be functionally, as distinct from how many years you have been alive. Tests use one of three methods: DNA methylation read from blood or saliva, algorithms built on routine blood biomarkers, or physical measures such as grip strength.
Cleveland Clinic frames biological age as accumulated cellular damage, and notes that it is not clear how reliable these tests are.[5] Every product here is a wellness product, not a diagnostic. The concept itself is unpacked in what biological age actually means.
How we review these tests
- Published instrument, named. We ask which clock or algorithm generates the number, and say so when a score cannot be traced.
- Effect sizes, not adjectives. A hazard ratio with a confidence interval beats "clinically validated".
- No kit of our own. We sell no test and take no vendor commission.
- Dated corrections. When the evidence changes, this page says when.
We have not run these kits ourselves. What follows reviews published validation data and vendors' own public claims.
How do I test my biological age?
Start with two free tests that take about ten minutes and have mortality data behind them. Write both numbers down with the date: that record beats one expensive score with nothing to compare it to.
Test 1: the sitting-rising test
Sit down on a bare floor, cross-legged, then stand back up. Score five points for sitting and five for rising. Deduct one point for each hand, knee, forearm or side-of-leg support, and half a point for a visible loss of balance.
Show the numbers as a table
| Measure | Value |
|---|---|
| Score 0 to 3 | HR 5.44 |
| Score 3.5 to 5.5 | HR 3.44 |
| Score 6 to 7.5 | HR 1.84 |
| Score 8 to 10 | Reference |
Those ratios come from 2,002 adults aged 51 to 80, followed for a median of 6.3 years (per de Brito 2014). Each point gained on the score was associated with a 21% improvement in survival.[2] The test is a proxy for strength, balance and flexibility, not a diagnosis.
Test 2: grip strength
Use an inexpensive hand dynamometer. Take the best of three squeezes on each hand and record the higher hand.
In the PURE study across 17 countries, each 5 kg reduction in grip strength carried a hazard ratio of 1.16 for all-cause mortality (95% CI 1.13 to 1.20).[3] In that dataset, grip predicted death more strongly than systolic blood pressure.
Large multi-country cohort · replicated predictorTest 3: what your resting numbers say
Resting heart rate, blood pressure, waist-to-height ratio and a standard lipid and glucose panel are the raw inputs of the blood-biomarker family. Recent bloodwork already holds most of what a biological age calculator asks for; several free ones simply derive a published clock output from the values you type.
Free tests versus a paid clock, side by side
| Test | Cost | What it predicts | Published effect size |
|---|---|---|---|
| Sitting-rising test | Free | All-cause mortality | HR 5.44, lowest vs highest band[2] |
| Grip strength | Low, reusable | All-cause mortality, CVD | HR 1.16 per 5 kg[3] |
| Survey calculator | Free | Your self-reported habits | None published for the score |
| Methylation kit | Low hundreds of dollars | Marketed as cellular aging | Vendor test-retest data rarely published[1] |
What epigenetic clocks actually measure
An epigenetic clock reads methylation at selected CpG sites and feeds it into a trained algorithm. Which age it estimates depends on what it was trained against.
First-generation clocks, Horvath and Hannum, were trained to predict chronological age. PhenoAge and GrimAge were trained against health outcomes, and DunedinPACE estimates pace of aging instead. The wider biology sits in the hallmarks of aging.
A clock that matches your birthday is not detecting health
If a first-generation clock returns an age within a year of your chronological age, that is the model hitting its training target, not evidence you are aging normally. Ask which clock produced your number before reading anything into it.
How accurate is a biological age test?
Less reproducible than the price implies. The same DNA, split and run twice with no biology changing, could return two numbers years apart.[1]
Show the numbers as a table
| Measure | Value |
|---|---|
| Standard clocks | Up to 9 years |
| PC clocks | About 1 year |
Why a before-and-after kit result can mislead you
If the assay alone can move your score by several years, a retest six months after starting a supplement cannot show whether the supplement did anything. The drop you see may be the lab, not you.
The same study shows the fix exists: retrained principal-component clocks kept most replicates close together. So the question to ask a vendor is not how young you are, but which clock version they run and what their split-sample error is.
- What this does not say
- Measures laboratory reliability of the clocks studied; commercial tests may use other or proprietary clocks whose replicate error is unpublished.
You can split the same sample, run it twice, and get upwards of eight years difference in your epigenetic age.
What counts as a real change
A two-year improvement after six months of effort may be measurement error wearing a success story. Prefer a principal-component or pace-of-aging output, and leave enough interval that biology can outrun the assay.
Reproducibility problem · unreported by vendorsWhat is the most accurate biological age test available?
There is no defensible single answer. Researchers at the Max Planck Institute state that biological age cannot at present be measured accurately using a single test.[4]
Accuracy is also the wrong question for most buyers. When tracking an intervention, a slightly biased measure that repeats consistently beats an unbiased one that scatters by years.
Is there a free online biological age test?
Yes, several, and most are questionnaires rather than measurements. They convert self-reported habits, height and weight into an age, so they inherit every optimism in your answers.
- Good for: motivation, and a prompt to look at habits you already know about.
- Bad for: judging whether something you changed worked. The floor test above is free and measures something.
The kits people actually buy
| Provider | Method | What they claim | Evidence status |
|---|---|---|---|
| TruDiagnostic | DNA methylation, blood | Biological age, speed of aging, organ-level scores | Organ resolution is a vendor claim; no test-retest data on the page |
| NOVOS ENABL Age | Survey-based | Greater accuracy than first-generation blood tests | No head-to-head comparison offered |
| AgelessRx calculator | Derived from your blood results | DNAm PhenoAge from values you enter | Names the published clock it uses |
| Function Health | Broad biomarker panel | Age readout alongside a lab panel | Value is mainly the panel |
Claims are summarized from each provider's public pages as observed in August 2026. Naming a vendor is not an endorsement, and no link here is affiliate-monetized.
How much does a biological age test cost?
Consumer methylation kits generally sit in the low hundreds of dollars per test, and most providers push a retesting subscription. Survey calculators are free. Insurance does not cover wellness testing, and HSA or FSA eligibility depends on your plan, so verify before ordering.
Nobody checks that the score means anything
After a federal court in Texas struck down the FDA's rule for laboratory-developed tests, consumer kits run as lab services answer to laboratory quality standards, not to a regulator asking whether the age they report predicts health.
A certified lab can measure methylation precisely and still sell you a number with no demonstrated meaning. Validity rests on the company's own publications, which is why the questions below matter.
- What this does not say
- US only; CLIA certification covers analytical quality of a lab, and some tests may be marketed in ways that still attract FDA or FTC action.
Questions to ask before you buy a kit
- Which published clock generates my number, by name?
- What is your test-retest reliability on split samples, in years?
- Is the sample blood or saliva, and which was the clock validated on?
- What size of change, over what interval, would you call real?
- What does any organ-level breakdown rest on?
A provider that answers all five is worth considering. One that answers none is selling a number, not a measurement.
What actually moves the number
Smoking status carries the largest single signal in outcome-trained clocks. Fitness, body composition and sleep move biomarker-based scores, and grip and floor-test scores respond to training. The mechanism underneath is covered in how cellular senescence drives aging.
Using a test to judge an intervention
Baseline first, before you start; a result taken afterward has nothing to compare against. Then hold everything constant: same provider, clock, sample type and season. Rapamycin's own evidence base shows why one wobbly readout should not decide anything.
Who should not bother
- Anyone who would not change a thing based on the result.
- Anyone planning to retest monthly. You will read assay noise as progress.
- Anyone substituting it for clinical screening. Blood pressure, lipids and glucose are not optional; these tests are.
- Anyone who has not done the two free tests yet.
Should you buy one? An honest decision aid
- For a mortality-linked number today, free: do the sitting-rising test.[2]
- For measuring an intervention: buy reliability, a principal-component or pace-of-aging output from a provider that states its error.[1]
- For motivation: a free survey calculator is fine if you know it is a questionnaire.
- Choosing between a kit and a compound: see which longevity supplements have real data.
Informational only, not medical advice
Frequently asked questions about biological age tests
If I send the same sample twice, how far apart can the results be?
Years apart. In a Nature Aging study of technical replicates, standard epigenetic clocks returned results up to 9 years apart from the same DNA, while retrained principal-component versions kept most replicates within about 1 year. Ask a vendor which clock version it runs and what its split-sample error is.
Is there anything free that predicts mortality as well as a paid test?
Free and cheap measures have published mortality data that most kits do not. In the lowest versus highest score band, the sitting-rising test carried a hazard ratio of 5.44 for all-cause mortality, and grip strength 1.16 per 5 kg lower. Vendors of methylation kits rarely publish comparable test-retest or outcome data.
Does a lower number after starting a supplement prove the supplement worked?
No. If the assay alone can move a score by several years, a retest six months after starting something cannot separate the supplement from the lab. The drop may be measurement error. A retrained principal-component clock with published split-sample error is the minimum before reading any change as real.
At what age does your body age the most?
Different tissues decline on different schedules, which is part of why a single whole-body number is a simplification. For testing, the useful comparison is you against your own baseline, not against a population curve.
How much does a biological age test cost?
Consumer DNA methylation kits generally sit in the low hundreds of dollars, and subscriptions multiply that. Survey calculators are free. Insurance does not cover wellness testing, and HSA or FSA eligibility depends on your plan.
How often should I retest?
Rarely, and on a fixed protocol: same provider, same clock, same sample type, similar time of year. Retesting within a few months mostly measures the assay rather than your biology.
Are consumer aging tests FDA approved?
No. They are sold as wellness or laboratory services, not cleared diagnostic devices, and they do not replace blood pressure, lipid, glucose or age-appropriate cancer screening.
Which epigenetic clock does my test actually use?
Ask, because vendors rarely lead with it. Horvath and Hannum predict chronological age, PhenoAge and GrimAge were trained against health outcomes, and DunedinPACE estimates a pace of aging rather than an age.
What is the sitting-rising test and how do I score it?
Lower yourself to sit cross-legged on the floor and stand back up. Start at 10 points, deduct 1 for each use of a hand, knee, forearm or side of the leg for support, and deduct 0.5 for a visible loss of balance.
Does grip strength really predict how long you live?
It is one of the better-replicated simple predictors. In the PURE study across 17 countries, each 5 kg reduction in grip strength carried a hazard ratio of 1.16 for all-cause mortality, a stronger signal than systolic blood pressure in that dataset.
What change in my score counts as real rather than noise?
On a standard first or second generation clock, a two-year improvement may be entirely measurement error, given replicate deviations reported up to 9 years. Ask the provider for its own split-sample figures. If it cannot supply them, you cannot separate a result from noise.
Is a blood test or a saliva test better for biological age?
Blood is the sample type most published clocks were trained and validated on, and saliva introduces a different cell mixture. If you compare results over time, the more important rule is to keep the sample type constant.
Can you actually lower your biological age?
Outcome-trained clocks do respond to real changes, with smoking status carrying the largest single signal. Fitness, body composition and sleep move biomarker-based scores. Far less clear is whether moving the score moves the outcome it was built to predict.
Should I test before starting a longevity compound?
If you test at all for that reason, take the baseline before you start. Testing after the fact gives you a number with nothing to compare it against, the most common and most expensive mistake in this category.
What do I do with the number once I have it?
Treat it as one data point beside your clinical numbers, not above them. Record it with the date, the provider and the clock used, so a future result is comparable. If the number would not change anything you do, you did not need it.
Sources and how we checked them
5 sources, all link-checked; oldest check
- A computational solution for bolstering reliability of epigenetic clocks: implications for clinical trials and longitudinal tracking. Higgins-Chen AT et al. Nature Aging 2022;2:644-661.Technical noise produced deviations of up to 9 years between replicate samples across six prominent epigenetic clocks; principal-component versions agreed within about 1 year.Verified Sep 15, 2026
- Ability to sit and rise from the floor as a predictor of all-cause mortality. de Brito LBB et al. European Journal of Preventive Cardiology 2014;21(7):892-898.2,002 adults aged 51-80, median follow-up 6.3 years, 159 deaths; SRT score 0-3 carried a multivariate-adjusted hazard ratio of 5.44 (95% CI 3.1-9.5) versus 8-10; each 1-point gain conferred a 21% survival improvement.Verified Sep 15, 2026
- Prognostic value of grip strength: findings from the Prospective Urban Rural Epidemiology (PURE) study. Leong DP et al. The Lancet 2015;386(9990):266-273.17 countries; hazard ratio 1.16 (95% CI 1.13-1.20) for all-cause mortality per 5 kg reduction in grip strength, a stronger predictor than systolic blood pressure.Publisher blocks automated checks · last tried Sep 15, 2026
- What is biological age and how can you measure it?. Max Planck Institute for Biology of Ageing, 2026.States that biological age cannot at present be measured accurately using a single test.Verified Sep 15, 2026
- Biological age: what it is and how you can measure it. Cleveland Clinic Health Essentials, 2025.Mainstream clinical framing; notes it is not clear how reliable commercial tests are.Verified Sep 15, 2026
Every link above is re-requested on a schedule by an automated checker; the date shown is when it last answered. Publishers that block automated requests are marked as such rather than reported broken. Our editorial standards explain how a source gets cited here in the first place.
Filed by the Rapamycin.store evidence desk. Each source is re-checked when the page is reviewed.
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