Published April 3, 2018
When an elderly man developed anemia, his physician advised the man’s daughter to give him 325 mg of ferrous sulfate (iron) tablets daily. Ferrous sulfate is taken to treat iron-deficiency anemia, a condition in which the body does not have enough healthy red blood cells due to low levels of iron in the body. The man’s daughter bought a bottle of “iron ferrous sulfate” from the pharmacy. The label said each tablet contained 65 mg (Figure 1), so she gave her father 5 tablets daily believing this would equal a 325 mg dose. However, each tablet actually contains 65 mg of elemental iron, which is equal to 325 mg of ferrous sulfate. Unfortunately, the label did not clearly state that each tablet contains 325 mg of <u>ferrous sulfate</u>. The information on the back of the label under Supplement Facts is also confusing. That part of the label says each tablet contains “Iron (as Ferrous Sulfate) 65 mg.” The elderly man developed severe constipation, a common side effect of iron even when given at the correct dose. He was soon hospitalized for other reasons. During his hospitalization, the mistake was recognized while reviewing the medicines the man had been taking at home.
This is not a new problem. Longstanding confusion with the way iron supplements are labeled has led to frequent errors. And it’s not just consumers who have made errors—so have healthcare providers, including nurses and pharmacists. Most physicians prescribe iron supplements as ferrous sulfate. Ferrous sulfate is the form of iron that is best absorbed by the body. As noted above, 325 mg of ferrous sulfate contains just 65 mg of elemental iron. Some iron supplement labels only list the amount of elemental iron in each tablet. Other iron supplement labels note that each tablet contains 325 mg of ferrous sulfate (Figure 2). However, mistakes have still been made because the Supplement Facts lists the amount of “Iron, as Ferrous Sulfate” in each tablet as 65 mg. Even worse, some liquid infant iron supplements do not include the amount of iron per mL at all on the front of the label (Figure 3). Instead, only the amount of elemental iron per mL is listed (15 mg), not the amount of ferrous sulfate per mL (75 mg).
In addition to ferrous sulfate, two other forms of iron supplements are available—ferrous gluconate and ferrous fumarate. Like ferrous sulfate, these forms of iron are easily absorbed in the body. But again, these products contain much smaller doses of elemental iron than ferrous gluconate or ferrous fumarate. For example, 240 mg of ferrous gluconate contains just 27 mg of elemental iron, while 325 mg of ferrous fumarate contains 106 mg of elemental iron. Although these iron-containing products are recommended less frequently than ferrous sulfate, the labels on these products are just as confusing.
Since most iron supplements are available over-the-counter (OTC), you may purchase them in any number of places without a pharmacist’s assistance. However, please consider the following recommendations to reduce the risk of an error:
