The concept of “biological age” has officially entered the mainstream.

From podcasts to TikTok to wellness newsletters, everyone seems to be talking about how old they really are — not by the number of birthdays they've celebrated, but by what’s happening inside their cells. Biological age testing promises to reveal how well you're ageing, whether your efforts to eat better, sleep more, or reduce stress are “working,” and whether you're adding years to your life — or life to your years.

And the appeal is obvious. In a world that’s increasingly focused on prevention and performance, the idea of quantifying your ageing process is both empowering and seductive. A simple test, a bold number, and the reassurance (or wake-up call) that you’re either thriving or falling behind.

But here’s the thing: while the science behind biological age is fascinating, these tests might not be telling you what you really need to know.

What Is Biological Age — and Can It Be Measured?

Biological age is meant to reflect the functional condition of your body — how well your cells, tissues, and systems are holding up over time. While your chronological age is fixed, your biological age is dynamic. It can be influenced by lifestyle choices, environmental exposures, stress, nutrition, and overall health.

At the heart of most biological age tests is something called epigenetics — the study of how your environment and behaviours affect the way your genes are expressed. Specifically, many of these tests analyse DNA methylation, a process where chemical tags (called methyl groups) attach to your DNA and influence how genes are turned on or off.

These patterns change with age and have been used to build what scientists call epigenetic clocks — algorithms that estimate biological age based on how your gene expression has shifted over time.

In controlled research settings, these clocks are showing real promise. Studies have found that epigenetic age can predict risk of mortality, cardiovascular disease, and certain cancers more accurately than chronological age alone. They’re also sensitive to lifestyle changes: smoking, poor diet, and chronic stress all tend to accelerate epigenetic ageing.

But things get more complicated out of a lab setting.

Where biological age testing falls short

While the research is encouraging, biological age testing in its current commercial form is still limited, especially when used at the individual level.

For one, there’s variability in the results. Studies have shown that two samples from the same person, taken at the same time, can yield different biological age readings, sometimes differing by as much as nine years. That means your “result” may not be as precise or reliable as it appears.

There’s also no universal standard for how biological age is measured. Different companies use different algorithms, data points, and lab methods - and most don’t disclose exactly how they arrive at your number. That makes it difficult to compare results or track meaningful progress over time.

But perhaps the biggest limitation is this: knowing your biological age doesn’t tell you why it’s higher or lower than expected, or what to do about it.

You might get a number. You might even get some generic lifestyle advice. But you’re not getting clarity on which of your systems are under strain. You're not being told whether it's inflammation, insulin resistance, poor detoxification, or hormonal dysregulation that's pushing your biology in the wrong direction.

And that’s where real action begins — not with a score, but with a signal.

What more useful ageing signals look like

Some measures of ageing are simply more actionable than others. Metrics that reflect functional capacity — rather than abstract age — tend to offer clearer direction. Aerobic capacity, often assessed through VO₂ max, is one such example. VO₂ max reflects how efficiently the heart, lungs, blood, and muscles deliver and use oxygen under load, and it consistently correlates with cardiovascular health, resilience, and long-term mortality risk. Unlike a biological age score, it measures capacity, not identity. It does not claim to tell you how old you are. It shows how well your system is functioning — and that capacity can be trained, tracked, and improved.

This distinction matters because when it comes to ageing well, numbers alone do not drive change. Signals do.

If you are still curious, some tests are better than others

For people who are scientifically inclined and interested in self-tracking, biological age testing can still offer value — as long as expectations are clear. Some providers are built with far more rigour than others.

TruDiagnostic and the Elysium Index stand out for their research foundations and transparency. TruDiagnostic draws on multiple advanced epigenetic clocks widely used in academic research and provides a broader set of ageing-related metrics beyond a single score, including pace of ageing and immune system ageing. Elysium’s Index test uses the DunedinPACE model, which focuses on the rate at which you are ageing rather than an estimated biological age, based on long-term longitudinal data.

Even so, these tests remain proxies, not diagnoses. They describe trends, not causes.

We Already have better tools to understand how we are ageing

At Biolume, we believe that personalised health shouldn’t be about vague metrics or one-size-fits-all advice. It should be about understanding what’s happening inside your body, in detail, so you can make meaningful, measurable changes.

Biological age may one day become a powerful tool. But right now, we already have access to better, more specific ways to understand how well you're ageing:

Are you inflamed? Check hsCRP, Amyloid A, and fibrinogen.
Are your metabolic pathways under pressure? Measure insulin, fasting glucose, HOMA-IR, and HbA1c.
Are your detox and antioxidant systems coping? Look at GGT, LDH, and markers like homocysteine.
Are your hormones balanced and responsive to life stage and stress? Track DHEAs, cortisol, testosterone, FSH/LH, and SHBG.
Is your cardiovascular system at risk? Start with ApoB, Lipoprotein(a), triglycerides, and HDL.
Are you nutritionally equipped to support cellular repair? Review vitamin D, zinc, magnesium, B12, and ferritin.

Each of these markers reveals something more precise than a broad biological age score ever could. And when tracked together over time, they show a much clearer picture of whether you’re ageing well, and where to intervene if you’re not.

So where does biological age sit right now?

While biological age testing is not inherently flawed, in its current consumer form, it lacks the precision, transparency, and actionability needed to guide meaningful health decisions. The underlying science is compelling, and in controlled research environments it continues to evolve, but for now we place it in the over-marketed hype basket.

Until the evidence improves — and until results can reliably explain why someone is ageing faster or slower, not just that they are — biological age remains more concept than tool.

Are You Really Ageing "Well"? Why Biological Age Tests Might Not Tell You the Whole Story