The Science

Where your numbers come from.

Every result in this app is measured against a range and read against your own baseline. This page explains each of those steps, names the evidence behind every Prime range, and defines the words the app uses. It is written to be checked: every source is linked, and a range with no source yet says so.

Glossary

The words the app uses, each defined once. The verdict words and the ranges are explained in full on the How it works tab.

ApoB (apolipoprotein B): One ApoB protein sits on every particle that can lodge cholesterol in an artery wall, so an ApoB count is a count of those particles. It predicts heart risk better than LDL cholesterol alone.
Attention: The verdict on a result that scores under 60: it sits well outside your Prime range. It is a prompt to talk to your provider, not a diagnosis.
Baseline: Your first reading of a marker on your record. Every later change is measured against it.
Biological age: Phenotypic Age: the age at which an average adult carries the same ten-year risk of death that your age and nine routine blood markers predict. A published measure (Levine and others, 2018), not an epigenetic clock.
Biomarker: Any measurable signal about your body: a blood test result, a wearable reading, a body measurement. Prime Years scores each one against a range.
eGFR: Estimated glomerular filtration rate, a calculation from your creatinine that says how well your kidneys filter. Above 90 is normal function.
Equilibrium dialysis: The reference method for measuring free testosterone. It reads about ten times higher than the direct immunoassay most laboratories use, so the two are never compared directly.
Evidence tier: Where a Prime range came from, on a ladder from a guideline threshold (the strongest) down to a population percentile (the weakest). Each marker on this page names its tier.
HbA1c: Hemoglobin A1c, the share of your red blood cells with sugar attached. Because red cells live about three months, it reflects your average blood sugar over that time.
Heart-rate variability (HRV): The small variation in time between heartbeats, measured by a wearable overnight. Higher generally means better recovery, but the number depends on the device and the metric it uses.
hs-CRP: High-sensitivity C-reactive protein, a marker of inflammation in the body. Below 1 mg/L is low cardiovascular risk.
Lab reference range: The range printed on your lab report, set by the laboratory that ran the sample. It answers “is this abnormal?”, which is a different question from “where should I aim?”. When a report carries one, it is the range shown beside your result.
N-of-1: Judging whether a therapy works by comparing you with yourself, before and after, rather than with a population average.
NHANES: The National Health and Nutrition Examination Survey, run by the CDC. A continuous survey of the US population that includes blood tests, and the population reference Prime Years uses.
Optimal: The verdict on a result that scores 85 or more: it sits inside, or very close to, your Prime range.
Population percentile: Where a value sits among the general population: a result at the 50th percentile is the median. It describes what is common, not what is healthy.
Prime range: A lab range answers “is this abnormal?”. A Prime range answers “where should I aim?”, and is set from published evidence. A result outside it is not the same thing as an abnormal lab result.
Protocol response: Whether a therapy is doing what it is meant to: the markers it targets are compared with your baseline, and the markers it could disturb are watched for safety.
Reference interval: The middle 95% of results in a defined healthy group. It is what a laboratory’s normal range is built from.
Safety marker: A marker a therapy can push the wrong way, watched while you are on it. Hematocrit on testosterone therapy is the classic example.
SHBG: Sex hormone-binding globulin, the protein that carries testosterone and estradiol in the blood. Only the unbound share is active, so SHBG decides how much of your total testosterone you can use.
Transferrin saturation: The share of your iron-transport capacity that is carrying iron right now. Read with ferritin, it tells iron deficiency from iron overload.
VO₂ max: The most oxygen your body can use at peak effort, estimated by a wearable. One of the strongest single predictors of how long you live.
Watch: The verdict on a result that scores between 60 and 84: outside your Prime range, but not far. Worth keeping an eye on.

Prime ranges, therapy checks and the biological-age model are decision-support tools, not a diagnosis. They do not replace your provider’s clinical judgment.