CBC won't show low ferritin. You can feel awful if your hemoglobin is OK but your ferritin is low.
DellaValle DM, Haas JD. Impact of iron depletion without anemia on performance in trained endurance athletes at the beginning of a training season: a study of female collegiate rowers. Int J Sport Nutr Exerc Metab. 2011;21(6):501-6. Accessed April 10, 2023. https://www.qxmd.com/r/22089308