From a global perspective, poor nutrition is the most important cause of iron deficiency and iron deficiency anemia. However, in developed countries gastrointestinal diseases are the most probable causes that should be taken into account in the differential diagnosis. Blood losses through mucosal ulceration, malabsorption, chronic inflammation, neoplasia, difficulties in intake of food, or a combination of these mechanisms can be found in various gastrointestinal diseases. Several iron compounds suitable for oral use are available, the most simple and most commonly used being iron salts such as iron sulfate or iron fumarate. However, oral iron is not always the best option. Intravenous (IV) iron has been shown to be effective in several observational and controlled studies. In cancer patients, oral iron has been shown to be effective in some studies, but IV iron has several advantages in this particular scenario: it is well tolerated, even in frail patients, and is quick to obtain a response, something rather convenient if prompt surgery is needed. IV iron is also widely used in chronic gastrointestinal blood loss caused by vascular malformations, a rather common scenario in patients on anticoagulant treatment. It is also relatively common in clinical gastroenterological practice to find anemia and iron deficiency in patients treated with nonsteroidal anti-inflammatory agents and/or antiplatelet drugs. IV iron is a useful and effective tool to treat iron deficiency in digestive diseases. Although we need more and larger trials to further define indications, protocols and follow-up rules in different pathologies, the available guidelines for the management of iron deficiency and anemia inflammatory bowel disease patients are good practical guides.