Supplements are usually prescribed to treat iron-efficiency anemia, such as an iron supplement or multivitamins. There are many forms of iron. Ferrous is more easily absorbed than ferric. Ferrous sulfate is cheaper and most commonly used. Some types of iron supplements contain vitamin C to aid absorption. Certain iron products that are more slowly absorbed or having coatings on them are less likely to irritate the digestive tract, but are slower to enter the body.