Iron (ingots on transferrin carts)Gates: ferroportin, set by the hepcidin dialRed cells from the marrow pressHepcidin is the body's iron gatekeeper: it closes the export gates (ferroportin) on gut cells and on the cells that store iron. A pill of 60 mg of iron or more raises hepcidin for about a day, so the next day's pill is absorbed roughly 35–45 % less. That's why some people take pills every other day. Pills still work and are the right first step for many people.IV iron skips the gut gate: the infusion is taken up by the storage cells, which then hand iron to transferrin, the body's carts (each carries at most two iron atoms), for the marrow to build red cells. In this model, one 1000 mg infusion lifts ferritin to about 474 µg/L within a week, settling near 172 by week 7, while hemoglobin rises from 105 to about 130 g/L by week 8; on daily pills, hemoglobin also rises but ferritin stays near 19.A typical pattern for one modelled woman (65 kg, starting Hb 105 g/L, ferritin 8 µg/L), not a prediction. Your NP confirms yours with bloodwork, rechecked at 6–8 weeks; ferritin reads high for a few weeks after an infusion. Dose depends on weight and hemoglobin, and some people need a second infusion.