Basophils are the rarest of the white blood cells, and this test reports them as a share of all white cells counted in a complete blood count. They carry histamine and heparin and take part in allergic and inflammatory responses. Because their share is so small, the percentage speaks less about basophils themselves than about the balance of the white cell population as a whole.
No readings for this marker yet.
A raised share is most often seen with allergic and inflammatory conditions, chronic skin disease, and an underactive thyroid; a persistent and marked rise can accompany disorders of the bone marrow and is followed up rather than read on its own. A lowered share carries little meaning, since the normal count sits so close to zero that a fall cannot be measured reliably, though acute infection, stress, and corticosteroids can suppress it. A percentage also shifts whenever other white cell types rise or fall, so the absolute count is the more stable figure. One unusual result is a reason to repeat the count and discuss it with a doctor.
Recent infection, allergic flare-ups, stress, pregnancy, and corticosteroid or antithyroid medication all move the figure, and results vary between analysers and between manual and automated differentials. It is read alongside the rest of the white cell differential and the absolute basophil count rather than in isolation, and the platelet and white cell picture together matters when a marrow disorder is being considered.
Reference ranges are general adult values and depend on lab, assay, age and sex. For orientation, not diagnosis — discuss results with your doctor.