Recommended Supplement Dosage for Iron

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Elemental iron is the amount of iron in a supplement available for absorption. Because different supplements have varying types of elemental iron, your dosage recommendation varies. Elemental iron should be printed on the label for you, so you don’t have to calculate how much available iron your supplement has to offer.

Recommended Dietary Allowance

The recommended dietary allowance for iron depends on your gender. For men, the dosage remains at 8 milligrams per day throughout adulthood. If you are a woman, however, your required amount fluctuates. Up through age 50, you need 18 milligrams a day, according to the Food and Nutrition Board of the Institute of Medicine. During pregnancy you need 27 milligrams daily, which decreases to 9 milligrams if you decide to breast-feed. From age 51 on, you only need 8 milligrams per day.

Meeting the RDA through Supplements

Iron supplements are made with two types of the mineral: ferrous and ferric iron. Ferrous has the highest amount of elemental iron for absorption. To give you perspective, if you are a woman requiring 18 milligrams of iron daily, taking 55 milligrams of a ferrous fumarate supplement doesn't actually give you 55 milligrams of absorbable iron. In this case, you'll get 18.2 milligrams of elemental iron -- 100 percent of your recommendation. To meet 100 percent of your recommendation as a man, take 25 milligrams of ferrous fumarate, for example, which actually gives you 8.3 milligrams of absorbable elemental iron.

Tolerable Upper Intake Level

Iron has a set tolerable upper intake level, known as the UL for short. This is the highest amount you should consume in a one-day period, before you could start having negative side effects. Iron’s UL is 45 milligrams daily for all adults of all life stages, although your doctor could advise getting more than this for anemia treatment. You’re not likely to get too much from your diet, but you can easily go overboard on supplements. Acute problems, such as constipation, nausea, vomiting and feeling faint, can develop if you take more than 20 milligrams per kilograms of body weight, the Office of Dietary Supplements reports. In doses over 60 milligrams per kilograms of body weight, your organs could start to shut down, possibly leading to a coma or even death.

Therapeutic Dosage for Anemia Treatment

Iron-deficiency anemia, or abnormally low iron levels, affects oxygen transportation throughout your body, leaving you overly fatigued and weak. The typical supplement dosage for treating anemia is 150 to 200 milligrams each day, which amounts to 2 to 5 milligrams of iron per kilogram of body weight, states the American Society of Hematology. Don’t attempt to treat anemia on your own, though. Because iron can be incredibly dangerous in high doses, your doctor will have to prescribe a safe therapeutic amount for your needs.