Popular Health Testing Kits Could Have a Major Flaw

Consumer “biological age” tests have become a longevity-space status symbol. You spit or prick a finger, get a number lower than your birthday, post the screenshot, and feel like science is on your side.

I’m not against measuring things. I am against treating a single noisy number like a medical truth.

As of late 2024, the best public reality check I’ve seen comes from Dr. Matt Kaeberlein on the Optispan podcast. He did something most product marketing never does: he stress-tested the kits instead of trusting the brochure.

What he actually did

Kaeberlein reported running eight kits from four companies—TruDiagnostic, Elysium, Tally Health, and DoNotAge—with samples collected on the same day under the same conditions. If these products were measuring a stable biological property, you’d expect rough agreement.

He did not get rough agreement.

Results varied widely across companies, and more damningly, within the same company on the same sample. In one case he described two readings almost 13 years apart from the same test. That is not a rounding error. That is a different decade of life.

Chart from the podcast discussion: same person, same time window, multiple kits—the spread is the story.

The control that exposed the bias

Noise is one problem. Bias is another.

To probe whether the age a customer claims might influence the result, Kaeberlein described submitting samples under the fake name “Johnny Optispan” to Elysium and TruDiagnostic, with a claimed age of about 33.5 while his true age was about 53.5.

As he reported it:

• Elysium stayed relatively consistent with its other reading for the same biological sample.
• TruDiagnostic returned a biological age about 13 years younger in the “Johnny” case—a large swing on what should have been the same underlying material.

Again from the podcast: same samples, different claimed ages, very different story depending on the kit.

I’m not presenting this as an independent lab study I ran. I’m taking Kaeberlein’s reported experiment seriously as a consumer-facing stress test—and it should make anyone pause before rearranging their life around a single kit result.

The conflict of interest nobody likes to say out loud

Many of these companies also sell supplements and other “anti-aging” products. The test becomes the sales funnel: your number is “high,” here’s a stack; retest later; celebrate the delta; renew the subscription.

That does not prove every result is rigged. It does mean incentives are misaligned. When the same organization both defines your “biological age” and sells you the fix, you should demand more transparency about methods, replication, and quality control—not less.

Trust is not a brand aesthetic. It is open methods plus boring, repeatable numbers.

Where the tests might still help

Skepticism is not the same as total dismissal.

Kaeberlein also allowed—and I agree—that these kits could have motivational value. Some people need a scoreboard. If a flashy number finally gets someone to sleep, lift, walk, and stop drinking every night, that behavior change is real even if the clock is noisy.

The flip side is also real: a “bad” result can create stress, and chronic stress is not free. If a test leaves you anxious, obsessive, or supplement-shopping out of fear, it may be net harmful even when the marketing copy is glowing.

As of late 2024, my view is simple: optional curiosity tool for some people; poor foundation for self-identity or medical decision-making for most.

Epigenetics is one slice of aging

Even if these clocks were perfectly precise tomorrow, they would still be measuring one piece of a multi-part process. Epigenetic alteration is often framed as roughly one of the dozen or so hallmarks of aging—correlation-rich, mechanism-incomplete, and nowhere near the whole story.

The hallmarks of aging: epigenetic change is one spoke, not the whole wheel.

Lifestyle, environment, genetics, inflammation, mitochondrial function, strength, metabolic health—they all matter. Obsessing over epigenetic age can crowd out the boring variables that actually move how you feel and perform.

This is also why I side-eye influencer “I reverse-aged 8 years” content. If the same kit can spit out different numbers on the same day, selective posting is almost inevitable. The flattering result gets the carousel. The ugly retest does not.

What I’d actually do

If you’re curious, try a kit if you want. Treat it like a weather app for your DNA methylation pattern—interesting, imperfect, not destiny.

Do not treat it as:

• a diagnosis
• proof that a supplement stack “worked”
• a replacement for functional outcomes

Ask better questions instead: How is your energy? Strength? Sleep? Mood? Blood pressure, lipids, glucose control, fitness, recovery? Can you play with your kids without getting winded? Those answers are noisier in a different way, but they map more closely to a life worth living.

Eating well, training consistently, managing stress, sleeping enough—the unsexy stack still beats a dashboard full of unvalidated clocks. Kaeberlein’s episode is a useful reminder to be a critical consumer in a market that sells certainty faster than science can deliver it.

Bottom line

The research is fascinating. The consumer products, as of late 2024, are not ready to be your north star.

Sources

• Kaeberlein, M. Discussion of consumer epigenetic age testing kits on the Optispan podcast (2024). Primary source for the multi-kit and “Johnny Optispan” comparisons summarized above.