Circadian variation in reticulocyte counts and immuno-detectable erythropoietin titers.

SummaryImmunoreactive erythropoietin levels of serum and reticulocyte counts were measured in a group of normal subjects. Values fluctuated throughout the day. Maximal levels of reticulocyte counts and erythropoietin tended to occur in the afternoon and early evening but the times did not coincide in individual subjects.