Epigenetic Clocks, GlycanAge and TruAge: Rating the Biological Age Tests

By Dr. Farhan Abdullah, DO | Medical Director, Magnolia Functional Wellness | Southlake, TX

Every few weeks, somebody slides a phone across my desk and says, "Look, my biological age is 41, and I'm 52. Is that good?" Then, a month later, a different person shows me a report from a different company claiming they're older than their birth certificate says. Same kind of test. Opposite feelings. Neither of them knows what the number actually means.

I get it. Biological age tests are everywhere right now, and they're marketed with a confidence the science hasn't quite earned. As a physician at Magnolia Functional Wellness here in Southlake, I'm not against them. I order them for some patients. But I'm picky, and I think you should be too. So let's rate them the way I'd rate any lab: what does it measure, how well is it validated, and what would you do differently once you have the result?

First, What Are These Tests Even Measuring?

"Biological age" isn't one thing. It's a family of estimates, and each member of the family looks at a completely different slice of your biology. Lumping them together is how people end up confused when two reports disagree.

Roughly, there are three camps. The first reads chemical tags on your DNA, a process called methylation, and feeds the pattern into a mathematical model. Those are the epigenetic clocks. The second looks at sugar structures attached to antibodies in your blood, which is the glycan approach. The third skips the exotic stuff and uses routine blood chemistry, things like glucose, albumin, white blood cell count and C-reactive protein, to calculate a "phenotypic" age.

Different inputs, different models, different answers. A 52-year-old can easily score 45 on one and 55 on another. That doesn't mean one lab made a mistake. It means they asked different questions.

Epigenetic Clocks: The Best-Studied Option

If a test has a deep research record, it's almost always a methylation clock. They've been around long enough to have generations, and the generations matter.

The original was built by Steve Horvath. In a 2013 paper in Genome Biology, he described a multi-tissue predictor of DNA methylation age developed from roughly 8,000 samples across 82 datasets. It was a landmark, and it showed that methylation patterns track chronological age remarkably well across many tissue types. But here's the catch. A clock trained to guess your birth year is, by design, good at guessing your birth year. That's not quite the same as telling you how healthy you are.

The second generation tried to fix that. In 2018, Morgan Levine and colleagues published DNAm PhenoAge in the journal Aging. Rather than training against the calendar, they trained against a composite of clinical measures tied to lifespan and healthspan. The resulting clock predicted outcomes including all-cause mortality and physical functioning better than the first-generation clocks did. That's a meaningful step, because it moved the question from "how old are you?" to "how are you holding up?"

The newest wave measures speed instead of a snapshot. In 2022, Daniel Belsky and colleagues described DunedinPACE in eLife, a blood-based biomarker of the pace of aging built from two decades of follow-up on participants in the Dunedin cohort. The authors reported high test-retest reliability, and associations with morbidity, disability and mortality. Think of it as a speedometer rather than an odometer. It asks how fast you're aging right now, which is arguably the more useful question if you're trying to change something.

So where does that leave the shopper? If a company offers a methylation test, the first thing I want to know is which clock is inside the report. A report built on a 2013-style clock and a report built on a pace-of-aging measure are not the same product, even when the marketing looks identical.

How I'd Rate GlycanAge

GlycanAge looks at the structure of sugar chains, called glycans, attached to immunoglobulin G, an antibody circulating in your blood. The idea is that those sugar patterns shift with age and with chronic inflammation. A fingerstick sample is enough, which is a real convenience, and the inflammatory angle is appealing to anyone who has spent time in functional medicine, as I have.

My honest caveat is about the evidence base. Glycan work is real science, but it's a much smaller research field than methylation, with fewer large cohorts testing whether a glycan age predicts hard outcomes the way the methylation clocks have been tested. I couldn't verify a study I'd be comfortable citing to you today, so I won't pretend otherwise. My rating: interesting, plausible, promising for tracking inflammation over time, but I'd treat it as a conversation starter, not a verdict.

How I'd Rate TruAge and Similar Methylation Panels

TruAge is a consumer methylation test from TruDiagnostic, and it belongs in the epigenetic family above. That's a good sign on the science side, because the underlying approach has the deepest record. Companies in this space typically report several clock-based estimates, and some labs make newer measures such as pace-of-aging available.

The cautions are practical, not philosophical. Methylation tests vary from run to run, and different clocks can disagree within the same person. Your result can also shift with a recent illness, poor sleep or a rough week. A single number is a thin foundation for a big decision. And price matters. These panels often cost several hundred dollars, so ask yourself what you'd change if the result came back better or worse than you expected.

One more thing I'd flag: these tests were validated mostly in research settings, on research cohorts. Whether a given improvement in your score predicts a longer or healthier life, in you specifically, hasn't been proven in a trial of consumer testing. That's not a reason to skip them. It's a reason to hold the result loosely.

My rating: the strongest scientific footing of the consumer options, most useful when repeated no more than once a year, and best read as a trend, never a one-time grade.

Why Two Tests Can Disagree About the Same Person

This is the part that trips people up, so it's worth slowing down. Imagine you send blood to two different companies in the same week. One reports that you're three years younger than your birthday. The other says you're two years older. Did somebody mess up?

Usually not. Each model was trained on different groups of people, using different outcomes, with different mathematical tricks. One may be tuned to chronological age, another to mortality risk, another to the pace of change. Add normal day-to-day biology (a cold last week, a bad night of sleep, a long flight back from a work trip) and a bit of laboratory noise, and you'll see why a single score can wobble. The researchers behind the newer clocks have specifically worked on reliability for exactly this reason, which is why I pay attention to whether a company can tell me how repeatable its result is.

What I tell my patients is simple. Pick one test, use the same lab each time, and compare yourself only to yourself. A trend across two or three years means something. A comparison between two different reports does not.

The Unglamorous Contender: Routine Labs

Here's the part that doesn't get a splashy ad campaign. Many of the signals that drive those clocks, such as inflammation, blood sugar control, kidney function and blood counts, can be measured with ordinary lab work that I can order at a fraction of the effort. A fasting glucose, an A1c, a lipid panel, an inflammatory marker, a metabolic panel. Boring. Actionable.

When I look at a patient who's worried about aging, the questions I care about are blunt. Is blood pressure controlled? Is insulin resistance creeping in? What's the grip strength? How fast can they walk? Can they get off the floor without using their hands? Those results are less shareable on social media, but they connect directly to a plan. Nobody ever lifted a heavier deadlift because their epigenetic score improved by three years.

A Quick Scorecard Before You Spend Money

Whatever test you're considering, run it through five questions.

• What does it actually measure: DNA methylation, glycans, or routine blood chemistry?
• Which clock or algorithm is inside, and has it been tested against real outcomes like disability and mortality?
• Has the lab shown that repeat samples from the same person give similar results?
• Will the report tell you what to do next, or only hand you a number?
• If the result were bad, would your plan change? If it were great, would you stop doing anything?

If you can't answer that last pair, hold your wallet. A test that can't change your behavior is entertainment, and entertainment is fine, but it shouldn't be confused with medicine.

What Actually Moves the Number

Here's the encouraging bit. The levers behind a better biological age score are the same ones that have always mattered. Resistance training twice or three times a week. Cardiovascular fitness, including some hard intervals and plenty of easy aerobic work. Protein you actually hit. Seven or more hours of real sleep. Alcohol dialed way down. And yes, getting outside in the evening once the Texas heat finally breaks, because walking around Southlake Town Square after dinner beats most supplements I've ever been pitched.

For some patients, we also look at hormones, metabolic health and other medically supervised options, and those decisions belong in a full conversation about your labs and history, not in an app. You can read more about how we approach this on our longevity medicine page.

How I Use These Tests at Magnolia

In my practice, I treat biological age testing as a baseline and a motivator, not a diagnosis. For the right patient, someone who's already doing the basics and wants a more detailed look, a methylation panel can be a useful data point, ideally paired with standard labs and functional measures like strength and fitness. For a patient who isn't sleeping, isn't exercising and hasn't had bloodwork in three years, I'd rather spend that money on a complete workup.

That's the whole philosophy at Magnolia Functional Wellness. Start with what's known and actionable. Add the fancy stuff only if it earns its place. And never let a single number tell you how to feel about your own body. If you're curious which testing approach makes sense for you, we can sort that out together at our Southlake clinic.