Your numbers
Biological Age: The Number That Does Not Care How Old You Are.
Two people can both be 45. Their numbers can disagree by years.
Reviewed by Jeffrey Blue, MD · 2 min read · October 15, 2026
The short version
- An estimate of how old your measurements look against the average for your age and sex.
- It moves when your numbers move, which makes it a scoreboard for change.
- It is not a medical finding or a prediction of how long you will live.
Biological age is an estimate of how old your measurements look, compared with the average person of your age and sex. Your actual age only goes up. Your biological age can move in either direction, because it follows your numbers.
How it is worked out
There is no single blood test for it, and different companies use different methods. Ours starts from the measurements in your report: blood pressure, cholesterol, blood sugar and body composition.
Each one is compared with the national average for someone your age and sex, using a large U.S. health survey run by the CDC (NHANES) as the reference. Published research links each measurement to long-term risk, and those differences are converted into years. An exactly average person comes out at exactly their own age.
What it is good for
It turns four separate results into one number you can actually remember, and one you can watch. If your blood pressure comes down and your cholesterol improves, your biological age moves with them. That makes it a useful scoreboard for the changes you are making.
What it is not
It is not a medical finding and it is not a prediction of how long you will live. It is an estimate built from a handful of numbers, and it is only as good as the numbers that go into it. A younger biological age is not a reason to skip a checkup, and an older one is a reason to talk to your doctor, not to panic.
The point
Your birthday is fixed. Most of the numbers that drive your biological age are not. That is the whole reason to measure it.
Sources
- Centers for Disease Control and Prevention. National Health and Nutrition Examination Survey (NHANES).
- Lewington S, et al. Age-specific relevance of usual blood pressure to vascular mortality. The Lancet, 2002 (one of the studies behind the blood pressure curve).
- Global BMI Mortality Collaboration. Body-mass index and all-cause mortality: individual-participant-data meta-analysis of 239 prospective studies in four continents. The Lancet, 2016.
- Body By Numbers. The Optimal Standard: how grades and Biological Age are calculated.
This article is general information, not medical advice. Make decisions about your care with your own doctor.