From the gut to the bloodstream
Dietary iron comes as heme iron (from animal foods, well absorbed) and non-heme iron (from plant foods, less efficiently absorbed). Enterocytes in the small intestine take up iron, and the transporter ferroportin moves it into the blood. There it binds transferrin, the plasma protein that carries iron to tissues, especially the bone marrow for red blood cell production.
Storage and the hepcidin thermostat
Iron not in immediate use is stored bound to ferritin, mainly in the liver, spleen, and bone marrow. The body has no active route to excrete excess iron, so absorption is the main control valve. The liver hormone hepcidin governs that valve: when iron is abundant or inflammation is present, hepcidin rises and degrades ferroportin, reducing absorption and release. When iron is needed, hepcidin falls and more iron enters circulation. Both deficiency and overload cause harm, which is why iron supplementation should be guided by testing. General educational information, not medical advice.