What Is Biological Age — and Can You Lower It?

Biological age is an estimate of how well your body has aged at the cellular and physiological level, rather than the number of years since you were born. That birthday count is your chronological age. Biological age asks a different question: given your biology today, how old does your body look? In 2026, several test categories try to answer that, but each one comes with caveats worth understanding before you read too much into a single result.

This guide explains what biological age means, how it is estimated, and where the science is still honest about its limits. It is educational and not medical advice.

What is biological age, in plain terms?

Biological age is a model’s best guess at how aged your body is, based on biological markers rather than the calendar. It tries to summarise the wear, repair, and resilience in your cells and systems into one number you can compare against your chronological age.

The appeal is intuitive. Two people born on the same day can be in very different shape. One may have the cardiovascular fitness and lab markers of someone younger; the other may not. Biological age is an attempt to put a number on that gap.

It is important to hold this loosely. Biological age is an estimate produced by a model, and the model reflects the data and assumptions behind it. It is a useful lens, not a precise readout of your remaining time.

Biological age vs chronological age — what is the difference?

Chronological age is fixed and predictable. It advances one year every year, the same for everyone, and there is nothing to measure or interpret. Biological age is the variable counterpart, meant to reflect how aged your body actually is right now.

The difference between the two is where the interest lies. When biological age is estimated to be lower than chronological age, it is often read as a positive signal. When it is higher, it is treated as a prompt to look more closely. Either way, the comparison only matters if the underlying estimate is reliable.

For more on how this fits into the bigger picture of healthy years lived, see our guide on healthspan vs lifespan.

How is biological age measured?

Biological age is most commonly estimated in two ways: epigenetic clocks and blood-based composite scores. Both take measurable biology and translate it into an age-like number by comparing your pattern against patterns seen across large groups of people.

Epigenetic clocks look at DNA methylation, a layer of chemical tags that sit on your DNA and change in fairly patterned ways as you age. By reading the state of many of these tags, a clock estimates an age. This is the category most people mean when they talk about an “aging clock.”

Blood-based estimates take a different route. They combine standard laboratory markers, the kind you might already see on routine bloodwork, into a single score. The logic is that the combined pattern of these everyday markers carries information about underlying aging. If you want to understand the individual markers first, start with our guide on how to make sense of your bloodwork.

There are other research approaches too, but epigenetic and blood-based methods are the ones most likely to reach you as a consumer test.

Are biological age tests accurate?

Biological age tests are best treated as broad signals rather than precise verdicts. They can be informative, but accuracy and repeatability are still maturing, and a single number should not be over-interpreted.

A few honest limitations are worth knowing. Results can differ between testing methods, so two clocks may give you two different ages from the same biology. Results can also vary between samples, and in some cases even when the same sample is measured more than once. That variability matters when you are looking for a small change.

There is also the deeper question of meaning. A test can produce a confident-looking number, but the science is still working out exactly how well these estimates predict long-term health outcomes for any one individual. Population-level associations do not always translate cleanly to a personal prediction.

None of this makes the tests useless. It means the right posture is curiosity, not certainty. Track trends over time rather than chasing one reading, and pair any result with the rest of your health picture.

Can you lower your biological age?

Some research suggests that measured biological age can shift in response to changes in health and lifestyle. That is encouraging, but a lower number on a test is not the same as proven rejuvenation, and the honest answer is that the science is still developing.

The sensible interpretation is that the inputs to good aging are largely the well-established fundamentals. Things like sleep, movement, nutrition, and managing risk factors plausibly influence the markers these tests read. A test result can be a way to monitor that effort, not a shortcut around it.

Be wary of any claim that a single product or protocol reliably “reverses your age.” The number on a test is a measurement, and measurements can move for reasons that have nothing to do with true biological change. Treat improvements as a hopeful signal to confirm over time, not a finished result.

If you do test, decide in advance what you would do with a higher or lower number. A result is only useful if it informs a next step.

That last part is where most people get stuck. AMORTAL takes markers like these, alongside your bloodwork and wearables, and turns them into one safe, cited next action — see how it works.

---

This article is educational and not medical advice. Talk to a qualified clinician before making decisions about your health.