Hi, welcome, glad to hear that you found something that works.
What do you see as differentiating a "Ferritin Iron Deficiency" from the usual iron deficiency? I know that some people do not respond to oral iron supplementation and do respond to injections but the "why" escapes me for now. Just trying to keep my terminology straight.
In looking up Ferrlecit it says:
"Ferrlecit is an intravenous (IV) iron replacement product for the treatement of iron deficiency anemia in patients 6 years and older with chronic kidney disease receiving chronic hemodialysis (HD) and supplemental epoetin therapy."
Is that your situation?
Iron deficiency, like a lot of things, hits the elderly harder, and also special populations like those with heart failure and restless legs. It is associated with the general condition called "frailty".
"Current aspects of frailty
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4803240/
Results from recent studies increasingly suggest an association between immunosenescence, inflammation, and the development of frailty: The age-associated overall change of the immune system is called immunosenescence. According to Franceschi et al,35 inflammaging is part of the immunosenescence process, consisting of an age-associated upregulation of the inflammatory response, resulting in a low-grade proinflammatory state.4 This proinflammatory state is characterized by increased levels of inflammatory cytokines, such as IL-6, IL-1, TNFα, and IFNγ. These cytokines have been shown to rise with age36 and to be associated with the development of ACI32 and other age-associated diseases.37 The process of immunosenescence has been shown to result in increased vulnerability to infectious diseases as well as to susceptibility of inflammation-associated pathologies in connection with, eg, chronic kidney disease, cardiovascular disease, Alzheimer’s disease, or diabetes mellitus.2,4,38 A study by Chang et al2 on the association between inflammatory disease burden and frailty revealed that a higher inflammatory disease count favors the occurrence of frailty in older patients. The consequence of the constant proinflammatory state does not only increase susceptibility to age-related diseases but also makes older patients prone to faster progression of all age-associated diseases.
Before realization of these biochemical insights into the pathogenesis of frailty, the syndrome of frailty experienced a more clinical approach. In the context of geriatrics, frailty describes a decline in physical strength, lean body mass, and power, associated with decreased balance, decreased walking performance, and low activity."

From the same article
"Anemia is a frequent finding in older patients and has been shown to be associated with increased physical impairment,9,10 frailty,11 cognitive decline,12 depression,13 and mortality."

So iron deficiency is a broad topic with broad implications. Anything you can add to help other folks, like myself for instance, who have had a treatment resistant anemia my whole adult life, would be very useful