Most people, especially women, should be aware of iron intake and absorption. Eating vitamin C-containing foods along with the high-iron foods or taking an ascorbic acid supplement, even 50–100 mg., improves the absorption of iron in supplements. Protein foods improve absorption and usually have a higher iron content, so eating more of these foods, such as meats and legumes, as well as leafy greens, helps get more iron into the body.

Iron supplements are strongly recommended when there are increased requirements, as with teenagers and most women, especially with heavy or long menstrual flow and definitely during pregnancy and lactation, when iron needs may triple. Most men, however, unless there is some bleeding problem, do not require additional iron. When there is sufficient iron intake, more will not necessarily help; in fact, it could lead to problems associated with excess iron storage over a period of time.

The ferrous (2+) forms of iron, not the ferric (3+) state, are the forms to have in supplements. Ferrous sulfate is the most commonly prescribed form of iron, although ferrous fumarate and gluconate are also prescribed by doctors. As an example, 325 mg. (5 grains) of ferrous sulfate contains about 120 mg. of elemental iron. With at least a 10 percent absorption rate, that allows more than 12 mg. of iron per tablet to get into the body; if these are taken several times daily in pregnancy or in anemia, as some doctors recommend, this may be excessive.

To improve iron absorption, take the iron with 250 mg. of vitamin C and between meals, if tolerated. During pregnancy, the increased need will also improve the percentage absorbed. Ferrous sulfate is often used because it is inexpensive and fairly assimilable for most women, though it can also be irritating to the gastrointestinal tract and cause constipation or blackening of the stools, which could cover up an intestinal bleeding problem (blood in the stool can also cause it to be black). Ferrous gluconate and fumarate are considered organic irons (as found in living tissues) and are also inexpensive and have good absorption, and they tend to cause fewer symptoms (constipation, intestinal upset) than the inorganic ferrous sulfate. The dosages are similar; 325 mg. of ferrous gluconate taken two or three times daily during pregnancy or to treat iron deficiency or blood losses. These amounts should not be taken regularly as a preventive or safeguard.

The form that probably is best assimilated and easiest on the intestinal tract is the hydrolyzed protein chelate of iron—that is, "chelated" iron. Usually about 50 mg. of chelated elemental iron taken once or twice daily will satisfy most iron needs during pregnancy or with iron deficiency. This can be used until the iron and red blood cell levels are normalized. The choice of form for iron supplements is based on absorption and gentleness. In order of preference, the suggested forms are chelated iron, such as iron aspartate, ferrous succinate, and ferrous fumarate, followed by ferrous gluconate and ferrous lactate. Ferrous sulfate is commonly used but produces more symptoms than the other forms.

There is some concern about vitamin E's interaction with iron. It can bind the iron to a nonutilizable form, which then can oxidize and thus inactivate the vitamin E when the two are taken together, though this occurs more so with the ferric forms of iron. Ferrous sulfate has some interaction with E. The organic forms of iron—gluconate, aspartate, and fumarate—as well as the chelated iron have little effect on reducing vitamin E. But, to be safe, it is best not to take vitamin E with iron but to take it by itself at night or in the morning.