How Much Iron Supplement Is Too Much?

Iron is a metallic mineral found in every cell in your body. It may well have been the first mineral to be incorporated into living tissue. Most of your body's iron is incorporated into your red blood cells, where it serves as part of the hemoglobin molecule, which is responsible for carrying oxygen through your bloodstream. Without sufficient iron, a condition called iron-deficiency anemia develops, resulting in fatigue, poor exercise tolerance, dizziness, decreased mental acuity and other symptoms. Many people take iron supplements to avoid iron deficiency.

Iron Absorption

According to Dr. Elson Haas, a physician and nutritionist, your intestine only absorbs 8 to 10 percent of the iron in your diet. The absorption of iron from your intestine is influenced by several factors, including your body's need for iron at any point in time. Two forms of iron are present in foods: heme iron, which is present in flesh and organ foods, and non-heme iron, which is found in dark leafy greens and other plant foods. Heme iron is much more efficiently absorbed than non-heme iron. Iron supplements are absorbed with varying levels of efficiency.

Daily Iron Needs

Daily requirements for iron vary considerably, depending on your age and gender. Infants need about one-quarter milligram each day, while pregnant females require 27 mg. Menstruating women lose iron every month, while healthy adult males and women who take contraceptives lose very little on a day-to-day basis. Growing children need more iron than those who are between growth spurts. Vegans need nearly twice as much iron in their diet as non-vegetarians of the same age. Supplements are recommended when your body needs more iron, but many people do not need more iron than their diets supply.

Iron Overload

Nearly all of the iron in your body is combined with some kind of protein, such as hemoglobin, transferrin, ferritin or myoglobin. Once all of these proteins are carrying their full capacity of iron, any excess must be stored in your tissues, which causes oxidative injury and chemical reactions that damage your liver, pancreas, gonads, heart and joints. A classic example of iron overload is a disease called hemochromatosis, which causes heart and liver damage, diabetes and reproductive problems. Acute toxicity from iron overload can also occur. For example, a child who consumes more than 3gm of iron at once -- as few as ten 300mg tablets -- can die from iron poisoning.

How Much Iron Is Too Much?

The symptoms of chronic iron overload, which might result from the daily consumption of unneeded supplements, can develop insidiously. Fatigue, joint pain, impotence, abnormal heart rhythms, depression, thyroid failure and mental problems can all be attributed to other causes. In 2000, the National Academy of Sciences established a tolerable daily upper limit, or UL, for iron at 45 mg. ULs and RDAs can be confusing, because they apply to the amount of elemental iron that you acquire from your diet or a supplement. For example, 325 mg of ferrous sulfate, a commonly used supplement, contains about 120mg of elemental iron. If you absorb 10 percent of that, you are getting 12 mg of elemental iron from each tablet. Hence, four of these tablets exceed the UL.

Considerations and Recommendations

Iron deficiency anemia is not an uncommon problem, especially among growing children, menstruating females and pregnant women. Supplemental iron is often needed in these groups. However, iron overload can be a serious condition, too, so not everyone should take supplemental iron. In fact, the iron in an over-the-counter multivitamin could be too much for a healthy adult male. If you think you need extra iron in your diet, talk to your physician about checking your iron status.