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Objective: Several biomarkers have been reported to exhibit a seasonal variation, which might also be associated with the seasonality observed for certain disorders, such as cardiovascular disease. Ferritin is a marker of iron stores but may be influenced by other factors including inflammation. The aim of this study was to determine whether there is a seasonal variation for plasma ferritin.

Methods: The study included all ferritin tests performed on blood donors between November 2009 and November 2016 in the county of Uppsala, Sweden.

Results: Median ferritin values were found to be highest in August to October (autumn) and lowest in April to May and December. The differences between the highest and lowest median values were 6 µg/L for males and 5 µg/L for females. This corresponds to approximately 12% difference for males and 15% difference for females.

Conclusion: A modest but statistically significant seasonal periodicity for ferritin was shown for blood donors.