Stability of serum ferritin in healthy subjects.

Recognition of chronobiological rhythms is important for the optimum use of blood parameters in clinical practice. The variation in serum ferritin, serum iron and total iron binding capacity was studied on two consecutive days in 16 healthy subjects. While serum iron changed in a typical circadian rhythm, no significant rhythm was found for serum ferritin or the total iron binding capacity. The daily intra-individual variation in serum ferritin was 15% on the average. The 24 hour mean serum ferritin concentration differed less than 5% in most of the subjects. In contrast to serum iron, there is no need to standardize the time of blood sampling for the determination of serum ferritin.