Haemosiderin and ferritin are the primary storage proteins for iron, respectively. As a result of chronic anaemia, low ferritin levels often indicate depletion; on the other hand, elevated levels signify iron overload disorders such hemochromatosis or are a result of repeated transfusions. Since ferritin is an acute phase reactant, an elevated level in an inflamed or inflammatory state could theoretically "mask" an anaemic condition. In order to better optimise patients before surgery and treat any severe deficiencies in a timely manner to prevent any acute consequences, it is crucial for bariatric surgery patients to examine their whole iron profile, including ferritin.