How to Test Your Biological Age

When we celebrate another trip around the sun, we’re recognizing our chronological age. But that’s only part of the picture. The more useful metric, especially if you’re hoping not only to live to a ripe old age but stay healthy and active at the same time, is knowing your biological age. So what’s the difference, and more importantly, how do you figure out how old you are on a biological level? Great questions! Let’s get to it.

What is biological age, and why does it matter?

You know the saying, age is nothing but a number? Well, it’s true—your chronological age is just a count of all the birthdays you’ve celebrated. Your biological age, on the other hand, is a reflection of something else entirely. It represents how well your body functions in comparison to other people in your chronological age group, taking into account everything from your fitness level and overall immunity to your cellular and organ function.

But does that even matter? Well, yes! Knowing your chronological age can mean qualifying for things like senior discounts and early bird specials, but there are benefits to knowing your biological age, too. It’s actually considered a far stronger predictor of longevity, health outcomes, risk of chronic disease, and even lifespan than chronological age alone.

Ever noticed why some 50 year olds look and act far younger than their years, while others look one or two decades older? That’s a reflection of biological age. Knowing yours is kind of like getting a little snapshot of how your body is actually aging. And that gives you opportunities to make changes that can improve not just your lifespan, but your healthspan. The only problem is that not all tests agree, which makes knowing how to interpret your results just as important as getting them (more on that later).

What factors influence biological age?

Now that we know biological age is a reflection of how your body is holding up as years pass, what’s actually moving the needle? It’s a mix of internal and external factors, and you’ll be pleased to learn that some of them are actually within your control.

• Genetics. We’ll start with what’s definitely out of your hands. The simple truth is that some people are just more resilient to things like inflammation and oxidative stress, and that plays a significant role in how they age. But that’s really only (a little less than) half of the story.
• Lifestyle choices. This is where you can make an enormous difference. The habits you cultivate every day, like diet, exercise, sleep, and stress management, actually have some of the most powerful effects on biological age. Consider it another reason to prioritize whole foods and antioxidants, strength training, sufficient sleep quality and quantity, and healthy outlets for stress.
• Metabolic health. Your body’s blood sugar regulation, insulin sensitivity, and lipid level affect your cellular health and, by association, your biological health. Happily, those responsible lifestyle choices we outlined above have a positive influence on metabolic health. It’s a two-birds-with-one-stone kind of scenario.
• Inflammation. Chronic low-grade inflammation, also known as inflammaging, is very closely tied to biological age. That’s because it contributes to age-related health conditions, like diabetes and cardiovascular disease. Again, what you eat and how much you move can make a big difference here.
• Cellular maintenance. A low biological age is characterized by efficient cellular processes, including DNA repair, mitochondrial function, and the timely clearing of zombie cells. When these kinds of things become slow and sluggish, biological aging accelerates. In addition to good nutrition, regular exercise, and quality sleep, longevity supplements like our own Wonderfeel Youngr™ can be a smart move for enhancing cellular repair. It supports NAD levels, which is directly linked to DNA repair and mitochondrial health.
• Environmental considerations. Poor air quality, alcohol, smoking, and UV radiation are also contributors to more rapid aging on a biological level. You can probably guess, but the best option here is to quit smoking, seriously limit alcohol, filter indoor air if you can, and limit your exposure to toxins by opting for safer cosmetics and cleaning products.

How is biological age measured—and why do different clocks show different results?

By now, you might be itching to learn your biological age—and we get it! But it’s not a matter of simple math. Biological age is an estimate based on different clues from your body, and there are different methods you may want to explore.

• Epigenetic clocks. These tests look at DNA methylation patterns, which change as you age. They’re currently considered the gold standard in biological age measurement.
• Blood biomarkers. Certain blood markers, including glucose, cholesterol, inflammation, and immune function, can be analyzed with algorithms to estimate biological age.
• Physical performance tests. Simple measures like grip strength, walking speed, and VO₂ max can shed a little light into how your body compares to others in your age group.
• Imaging and lab tests. Bone density scans, vascular imaging, or even telomere length analysis provide additional context, though these tend to be less predictive on their own.

Explore methods to measure biological age

While epigenetic clocks on their own are highly predictive, pairing them with blood biomarkers, fitness metrics, or imaging gives you more context. Together, they tend to paint a more complete picture of how your body is truly aging.

A few specific biological clocks have gained traction, and you might recognize some of the names behind them. They’re all doing things a little differently.

• The Hovarth Clock. Developed by Dr. Steve Hovarth and colleagues in 2013, this is the best-known DNA methylation-based epigenetic clock. It was the first widely validated model to estimate biological age across multiple tissues.
• The IC Clock. A blood-based epigenetic test from the Buck Institute that measures intrinsic capacity (that’s the World Health Organization’s framework for physical and cognitive ability over time).
• Eric Verdin’s immunity clock. Also at the Buck, this model combines data across immunity, biology, and metabolism for a more holistic look at aging.
• GlycanAge. A commercial test that analyzes sugar molecules (glycans) coating immune proteins, offering insight into inflammation and immune system aging.
• DNAm PhenoAge Clock (created by Morgan Levine) available here, TruDiagnostic also branded by Mark Hyman), and InsideTracker. Other consumer-facing companies offering biological age testing, typically using DNA methylation or blood biomarker panels.

Here’s the thing. These tests don’t always agree—and sometimes the differences are off by more than a few years. That’s why the same person might see wildly different results depending on the clock they’re using. To address this very issue, leading scientists came together at the Buck Institute in December 2023 to launch the Biomarkers of Aging Consortium. Their mission is to standardize, validate, and implement biological age measures so they can be compared more reliably and ultimately used in research, clinical trials, and personalized longevity strategies. Basically, they’re trying to figure out how to level the playing field here so that results are a little more trustworthy across the board.

Can I really test for my biological age?

You can, but maybe temper your expectations somewhat. Direct-to-consumer kits like the ones we mentioned above mean you can test at home, with a cheek swab, saliva, or blood sample that’s shipped off to a lab for analyzing. Some wearables and apps also use metrics like heart rate variability, sleep quality, or aerobic fitness to give you a general idea of your biological age. They’re not as precise, but they can still be useful for tracking improvements and changes over time.

Are biological age tests accurate?

Yes and no. The more sophisticated tests, like the epigenetic tests, are considered the more accurate way to assess biological age. Blood biomarker panels and performance tests can give you good information, but they can fluctuate based on things like diet, stress, and illness.

Another wrinkle is that different clocks—and the algorithms behind them—can return very different results for the same person—sometimes by more than just a year or two. For example, the Horvath Clock (the original multi-tissue DNA methylation model) might tell you one thing, while the PhenoAge clock, which captures disease risk, or the GrimAge clock, which predicts mortality risk, tell you something else. Add in other models like the IC Clock from the Buck Institute, which focuses on intrinsic capacity, or GlycanAge, which tracks immune system aging by analyzing glycans, and you start to see why results can diverge! It highlights the need for standardization, which is exactly how we ended up with the Biomarkers of Aging Consortium. Again, the mission is standardizing these tests, from development to validation to application, so that results can be trusted across labs, clinics, and consumer platforms.

At this point, the best approach is to think of biological tests as guides, not a source of definitive information. Obviously, they won’t tell you how long you’ll live, but they can offer insights into how your current lifestyle choices are affecting your health and whether that means you’re trending younger or older than your physical years.

Can I reduce my biological age?

If you’ve read this far, you already know the answer is yes. Your chronological age is fixed (even if you lie about it), but you really can slow down and even shave years off your biological age. So much of it comes down to the choices you make today, tomorrow, and onward. There’s no single magic bullet, just an intentional combination of the healthy behaviors we touched on above. At Wonderfeel, we think testing your biological age is most useful as part of a long-term strategy—think tracking progress over time while layering in evidence-based lifestyle and supplement interventions.

The most important part is staying consistent. Little things you can do every day really do add up over time. That’s actually why knowing your biological age is so important—it gives you a baseline, a measurable starting point, so you can track your progress as you slowly shift your habits.

The bottom line on testing biological age

Biological age gives you a far more meaningful picture of your health than chronological age alone. The best tests—particularly epigenetic clocks—offer actionable insights that you can use to track and improve your aging trajectory.

If you’re curious about your own biological age, go ahead and test! But ask yourself what you’ll do with the results, since that’s where real longevity gains are made. Pair your results with healthy lifestyle changes and retest periodically to see how your efforts are paying off. Think of it as feedback on your wellness strategy—one that can help you add not just years to your life, but life to your years.