Specialty Testing Guide › TruAge Biological Age Testing
TruAge is consistent enough to show large differences between people and large changes over time, but any single result carries some measurement noise. A shift of a year or so in biological age, or a few hundredths in pace of aging, can come from the test itself rather than from your body.
Accuracy also has two meanings here. One is whether the clocks predict health outcomes in large groups, where the evidence is fairly strong. The other is whether the same blood would give the same answer twice, which is where the caution sits.
Key takeaways
- Clocks such as GrimAge and DunedinPACE predict illness and death well across large populations.
- Technical noise can move an individual result, and older clock designs were especially affected.
- The lab's own reliability figure is useful but is not the same as independent testing of your single result.
- Only trust a change that is large, repeated, measured on the same report version and backed by other evidence.
Prediction: what the clocks get right
Epigenetic clocks were built and tested on thousands of people followed for years. GrimAge predicted time to death, coronary heart disease and cancer across large validation datasets. In a 2026 Berlin study of older adults that compared 14 proposed biomarkers of aging, DunedinPACE was the strongest predictor of death.1
That is real evidence, and it is why clinicians take these clocks seriously. But it describes groups. A clock can rank thousands of people well and still give any one person a result that moves around from test to test.
Where the noise comes from
TruAge reads methylation at more than a million sites on DNA from your blood cells using a microarray. Not every site on these arrays is measured equally well. A study that repeated measurements on the same 350 blood DNA samples found reliably measured sites behaved consistently, while unreliable ones were less replicable.
When a clock leans on unreliable sites, its output wobbles. Technical noise produced differences of up to 9 years between replicate measurements for six well-known clocks.2 Rebuilding those clocks from more stable summary patterns brought most replicates within 1.5 years of each other.
Newer clocks were designed with this in mind. DunedinPACE was developed from a dataset that excluded sites with low test-retest reliability, which is one reason it is often the steadiest number on the report.3
What the lab says about its own reliability
TruDiagnostic states on its website that TruAge has an average intraclass correlation coefficient above 0.98.4 That figure is the lab's own claim. An ICC measures how well repeat tests keep people in the same order; it does not tell you how many years your own number might drift between two draws.
Algorithms also change. The lab's sample report says that reports processed after November 10, 2025 use an updated platform and newly trained algorithms, and that this can cause minor differences that reflect the technology rather than your biology.5 Compare results produced on the same version wherever you can.
Biology adds its own variation
Because the test reads DNA from white blood cells, the mix of cell types in your blood can influence some results. TruAge estimates that mix and adjusts for it, which helps. Even so, it is sensible to test when you are well rather than during an infection, a flare of a chronic condition or right after surgery, and to keep conditions similar between tests.
When a change is probably real
- It is large: several years on an age clock, or a clear move in pace of aging, not a rounding difference.
- It is repeated: the next test points the same way.
- Several clocks agree: biological age, organ ages and pace move together.
- Other evidence fits: your weight, blood pressure, glucose or fitness changed in the same direction.
Even in a randomized trial, real effects were modest. Two years of calorie restriction slowed DunedinPACE, but the effect sizes were small and other clocks such as GrimAge did not change significantly.6 That sets realistic expectations for what a few months of changes can show. Our guide on how often to retest covers timing.
What accuracy cannot tell you
A reliable measurement is not the same as a proven target. There is little evidence yet that lowering your clock number changes what happens to your health. Use the result as one input to a plan, read alongside the rest of your report and your standard labs.
Your next step
If you live in Pennsylvania and want to know what testing through our Conshohocken clinic involves and costs, see TruAge cost in Pennsylvania, or browse the TruAge guide.
Frequently asked questions
If I sent two samples on the same day, would I get the same biological age?
Close, but not necessarily identical. Newer clock designs agree much better between repeats than older ones, yet a difference of a year or so is still possible.
Is pace of aging more reliable than biological age?
DunedinPACE was built to exclude unstable measurement sites, so it tends to be steady. It still has noise, so small changes deserve caution.
Does a high ICC mean my result is exact?
No. A high ICC means repeat tests rank people similarly. It does not give the margin of error around your own number.
Can I compare TruAge with a test from another company?
Not directly. Different companies use different clocks and methods, so numbers from one rarely line up with another. Track change within one lab and one report version.
Related reading
This article is for general education and is not medical advice. Decisions about testing and treatment should be made with your clinician. If you have severe symptoms, call 911. For a suspected poisoning, call Poison Control at 1-800-222-1222.
