Having a low hematocrit level is one of the most common reasons individuals are deferred from donating blood. Effective June 16, 2015, the blood donation deferral period for low hematocrit is extended from one day to 30 days.
It typically takes at least a few weeks of increased iron intake to affect an individual's hematocrit level. This policy gives donors time to increase their hematocrit levels by regularly eating iron-rich foods and incorporating an iron supplement into their routines.
More information about iron can be found at giveblood.org/iron.