Lymphocyte percentageLymphocyte %
The share of your white blood cells that are lymphocytes.
Lymphocyte percentage is the share of your white blood cells that are lymphocytes, the cells responsible for adaptive immunity: B cells producing antibodies, T cells coordinating and killing infected cells, and natural killer cells.
It is reported as a percentage alongside an absolute count, and the absolute count is generally the more useful of the two. A percentage can shift simply because another cell line changed, so a low lymphocyte percentage during a bacterial infection often reflects a surge in neutrophils rather than any fall in lymphocytes.
The usual pattern in adults is neutrophils dominating with lymphocytes as the second largest group, though the balance is reversed in young children, which is normal for them and misread surprisingly often.
Viral infections characteristically raise lymphocytes, while bacterial infections typically raise neutrophils. Prolonged stress, corticosteroids and some viral illnesses lower them, and marked persistent changes in either direction warrant investigation.
It appears in biological age scoring for this reason. The Phenotypic Age equation our calculator implements includes lymphocyte percentage among its nine blood markers, where it contributes as an indicator of immune status alongside inflammation and metabolic measures.
Hard exercise moves it transiently. Intense sessions produce a rise followed by a temporary dip, which is one contributor to the disputed idea of an open window of increased infection risk after prolonged hard training.
In practice, read the absolute count rather than the percentage where both are given, ignore small deviations in a well person, and take a persistent abnormality to a GP.
Sources
Where your own result would sit
Most people reading this page are holding a blood-test report with this marker on it, and the question they arrived with is whether their number is normal. A reference interval says where most results from a healthy population fall; a guideline threshold is where a clinical body draws a line for a decision. Neither is a target, and a result on the wrong side of one is not a diagnosis: the same number can be unremarkable in one person and worth looking into in another, which is why the clinician who ordered the test reads it against your history rather than against a list.
Lymphocyte percentage has no published interval on this page yet. We hold one, and the dashboard draws it beside a reader’s own result, but it has not been read back against the laboratory’s own page since it was collected. A figure printed beside somebody’s blood result has to have been seen at its source, not remembered, so this one waits.
On your own blood test?
Lymphocyte percentage is one of the markers FitTools can read from an uploaded blood-test report. You confirm every value before anything is saved, and your results are explained together in one place.