A biological age test estimates how your body is functioning, expressed in years. The result usually comes from a formula that compares your blood values against those of your peers. A score of 34 when you are 42 does not mean your organs are 34 years old. It means a handful of markers look better than average.
I have mixed feelings about it. The underlying science is decent, but the way the result gets sold often is not. A score is not a diagnosis, and it certainly is not an age.
What follows is the explanation I wish I had read before ordering one.
What is biological age exactly?
Biological age is a calculated estimate of your functional state. It rests on measurable markers such as inflammation, blood sugar regulation, kidney function and blood lipids. Your chronological age, also called your calendar age, is fixed. Your biological age is a snapshot. It shifts with your lifestyle, your training load and even a recent infection.
The idea comes from research into ageing at the cellular level. Researchers looked for markers that predict how someone fares better than a birth year alone. That worked, but at group level.
That distinction matters. A model that predicts well across a thousand people can still be well off for you personally.
A biological age gives you a direction, not a diagnosis. The number says something about your risks at group level. The individual markers beneath it can give you real insight into where you stand. Those show you which dial you can turn yourself.
How do you find out your biological age?
There are roughly three routes. A blood model converts routine markers into a score. An epigenetic clock measures DNA methylation. A fitness estimate is based on performance. They do not measure the same thing and they are not equally reliable. The blood route is the best supported and the cheapest. The epigenetic route sounds the most exciting.
The best known blood based method is PhenoAge, developed by Levine and colleagues. It combines nine routine markers with your age (PMID 29676998). Horvath's epigenetic clock measures something quite different, namely methylation patterns on your DNA (PMID 24138928).
| Method | What it measures | Strength | Weakness |
|---|---|---|---|
| Blood model (PhenoAge style) | Albumin, creatinine, glucose, hs-CRP, lymphocytes, MCV, RDW, alkaline phosphatase, white cells | Cheap, repeatable, every marker can be acted on | Sensitive to a cold or a heavy training week |
| Epigenetic clock | DNA methylation at hundreds of sites | Predicts strongly at group level | Expensive, and test to test noise can exceed the effect you want to see |
| Fitness estimate | VO2max, grip strength, recovery rate | Measures function, not chemistry | Says little about inflammation or blood sugar |
See the pattern? Each method measures a different part of the elephant.
Which blood values weigh the most?
In almost every blood model, inflammation and blood sugar regulation carry the most weight. A raised hs-CRP pushes your score up, as does a climbing HbA1c. Albumin and the red cell picture count too, but they move more slowly. That makes inflammation and glucose the two dials worth turning first.
This is no accident. Chronic low grade inflammation runs like a thread through almost every model of ageing (PMID 30065258).
To understand why that one marker weighs so heavily, read what hs-CRP says about ageing. If blood sugar is your weak link, the full story sits in measuring metabolic health.
Why do athletes often score strangely on these tests?
Because the formulas are built on the average population, and you are not that. Training changes precisely the markers the model uses, and not always in the direction the model expects. A well trained man can end up with a worse score than his untrained neighbour. He may be fitter all the same.
Four distortions show up most often.
- Creatinine. A lot of muscle mass means structurally higher creatinine. The model reads that as poorer kidney function.
- Hs-CRP after a hard session. A tough lifting session or a long run can lift your hs-CRP for days.
- Haematocrit. Endurance training at altitude, or simply being well trained, shifts your red cell picture.
- Alkaline phosphatase. Bone turnover after repeated impact can nudge this value up.
Picture two men of 42. One trains four times a week. Two days after a heavy leg day his creatinine is 105 micromol per litre. His hs-CRP sits at 2.8 mg/l.
The other does not train and sits at 78 micromol per litre and 0.9 mg/l. The model still hands the athlete the older score. In reality that says more about muscle mass and training timing than about ageing.
This is why I never read a biological age score on its own. The underlying list of markers is genuinely useful. The number above it is marketing.
Can you lower your biological age?
The markers the score is built from can certainly move. Inflammation, blood sugar and lipids respond to sleep, food, alcohol and training load, sometimes within months. Whether that means you are "ageing more slowly" is a different question. The evidence there is far more cautious than the advertising suggests.
RIVM, the Dutch national institute for public health, tracks how lifestyle relates to health in later life. Those figures are more sober than most providers' promises.
My advice: steer by the individual markers, not by the number.
What do you do with the result?
Test fasted, and avoid testing within three days of a hard session or an infection. Then look at the underlying markers rather than the composite score. Always compare a new measurement against your own previous one. The trend inside your body tells you more than an average does.
To see those markers in context, look at a broad panel. The 360 Health blood test covers inflammation and blood sugar. It covers kidney function and lipids in the same run. The wider picture sits in the guide on healthy ageing as an athlete. The muscle side of the story sits in sarcopenia after 40.
If you order a biological age test, do it to see the markers. Not to see the number.
References
- Levine ME et al. An epigenetic biomarker of aging for lifespan and healthspan. Aging (Albany NY), 2018. PMID 29676998
- Horvath S. DNA methylation age of human tissues and cell types. Genome Biology, 2013. PMID 24138928
- Ferrucci L, Fabbri E. Inflammageing: chronic inflammation in ageing, cardiovascular disease, and frailty. Nature Reviews Cardiology, 2018. PMID 30065258
- RIVM, Public Health Foresight Study, lifestyle and health.
Every blood test result includes a professional assessment from a BIG-registered doctor. For treatment decisions, discuss your results with your GP.
To see what your values add up to, use the biological age calculator.
Frequently asked questions
Can I work out my age myself?
Your calendar age, yes. Your biological age, not without measured values. Online questionnaires estimate it from sleep, food and movement. That gives an indication, not a measurement.
For a calculation based on blood values you need a laboratory result. Without those numbers the formula has nothing to work with.
How can I calculate the age of my body?
There are three routes: a blood model, an epigenetic clock and a fitness estimate. The blood model is the best supported and the cheapest. It converts routine markers such as hs-CRP, glucose and albumin into a score.
Test fasted, and not within three days of a hard session or an infection. Both lift your inflammation value temporarily.
What is my real age?
Your real age is your chronological age, and that is fixed. What a test estimates is your functional state right now.
The two often diverge, in both directions. Read the number as a snapshot, not as an age.
At what age do you age fastest?
There is no single answer to that. Ageing markers do not move at the same moment in everyone.
What does stand out is the spread. After forty, people of the same age drift further apart. Your own trend across two measurements therefore says more than your age group.
Author
Enhanced Health
Dr. Naimi, BIG-registered physician, oversees the medical standards behind our content and assessments. Read our medical policy
