Iron is pervasive, but particularly rich sources of dietary iron include red meat, lentils, beans, poultry, fish, leaf vegetables, watercress, tofu, chickpeas, black-eyed peas, blackstrap molasses, fortified bread, and fortified breakfast cereals. Iron in low amounts is found in molasses, teff and farina. Iron in meat (heme iron) is more easily absorbed than iron in vegetables.^[59] Although some studies suggest that heme/hemoglobin from red meat has effects which may increase the likelihood of colorectal cancer,^[60][61] there is still some controversy,^[62] and even a few studies suggesting that there is not enough evidence to support such claims.^[63]

Iron provided by dietary supplements is often found as iron(II) fumarate, although iron sulfate is cheaper and is absorbed equally well. Elemental iron, or reduced iron, despite being absorbed at only one third to two thirds the efficiency (relative to iron sulfate),^[64] is often added to foods such as breakfast cereals or enriched wheat flour. Iron is most available to the body when chelated to amino acids^[65] and is also available for use as a common iron supplement. Often the amino acid chosen for this purpose is the cheapest and most common amino acid, glycine, leading to "iron glycinate" supplements.^[66] The Recommended Dietary Allowance (RDA) for iron varies considerably based on age, gender, and source of dietary iron (heme-based iron has higher bioavailability).^[67] Infants may require iron supplements if they are bottle-fed cow's milk.^[68] Blood donors and pregnant women are at special risk of low iron levels and are often advised to supplement their iron intake.^[69]