Having extremely low ferritin, when you are not clinically anemic, is a specific type of anemia called Hypoferritinemia without Anemia or HWA. There is no kidney involvement and there are no other clinical issues like typical iron deficiency causing anemia.
It typically goes undiagnosed, and can cause permanent damage!
Links to resources mentioned:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5986027/
https://www.bmj.com/content/326/7399/1124
