One preliminary study found iron levels to be reduced after both minor and major surgeries, and iron supplementation prior to surgery was not able to prevent this reduction.¹ A controlled trial found that intravenous iron was more effective than oral iron for restoring normal iron levels after spinal surgery in children.² One animal study reported that supplementation with fructo-oligosaccharides (FOS) improved the absorption of iron and prevented anemia after surgery,³ but no human trials have been done to confirm this finding. Some researchers speculate that iron deficiency after a trauma such as surgery is an important mechanism for avoiding infection, and they suggest that iron supplements should not be given after surgery.⁴

Patients who have undergone major surgery frequently need blood transfusions to replace blood lost during the procedure. Studies have found that 18 to 21% of surgery patients were anemic prior to surgery,^5,6 and these anemic patients required more blood after surgery than did non-anemic surgery patients. Supplementation with iron prior to surgery was found in a controlled trial to reduce the need for blood transfusions, whether or not iron deficiency was present.⁵Iron supplements (99 mg per day) given before and for two months after joint surgery in another controlled trial improved blood values but did not change the length of hospitalization or the risk of post-operative fever.⁸ Pre-operative iron supplementation in combination with a medication that stimulates red blood cell production in the bone marrow is considered by some doctors to be an effective way to minimize the need for post-operative blood transfusions.⁹

Iron deficiency is often present in HIV-positive children.¹⁰ While iron is necessary for normal immune function, iron deficiency also appears to protect against certain bacterial infections.¹¹ Iron supplementation could therefore increase the severity of bacterial infections in people with AIDS. For that reason, people with HIV infection or AIDS should consult a doctor before supplementing with iron.

Caution: People should not supplement with iron unless diagnosed with iron deficiency, because taking iron when it isn’t needed has no benefit and may be harmful.

Before iron deficiency can be treated, it must be diagnosed and the cause must be found by a doctor. In addition to addressing the cause (e.g., avoiding aspirin, treating a bleeding ulcer, etc.), supplementation with iron is the primary way to resolve iron-deficiency anemia.

If a doctor diagnoses iron deficiency, iron supplementation is essential. Though some doctors use higher amounts, a common daily dose for adults is 100 mg per day. Even though symptoms of deficiency should disappear much sooner, iron deficient people usually need to keep supplementing with iron for six months to one year until the ferritin test is completely normal. Even after taking enough iron to overcome the deficiency, some people with recurrent iron deficiency—particularly some premenopausal women—need to continue to supplement with smaller levels of iron, such as the 18 mg present in most multivitamin-mineral supplements. This need for continual iron supplementation even after deficiency has been overcome should be determined by a doctor.

Since blood is rich in iron, excessive blood loss can lead to iron depletion. Iron deficiency can be identified with simple blood tests. If an iron deficiency is diagnosed, many doctors recommend 100–200 mg of iron per day, although recommendations vary widely.

The relationship between iron deficiency and menorrhagia is complicated. Not only can the condition lead to iron deficiency, but iron deficiency can lead to or aggravate menorrhagia by reducing the capacity of the uterus to stop the bleeding. Supplementing with iron decreases excess menstrual blood loss in iron-deficient women who have no other underlying cause for their condition.^13,14 However, iron supplements should be taken only by people who have, or are at risk of developing, iron deficiency.

Iron requirements increase during pregnancy, making iron deficiency in pregnancy quite common.¹⁵ Iron supplement use in the United States is estimated at 85% during pregnancy, with most women taking supplements three or more times per week for three months.¹⁶ Pregnant women with a documented iron deficiency need doctor-supervised treatment. In one study, 65% of women who were not given extra iron developed iron deficiency during pregnancy, compared with none who received an iron supplement.¹⁷ However, there is a clear increase in reported side effects with increasing supplement amounts of iron, especially iron sulfate.^18,19 Supplementation with large amounts of iron has also been shown to reduce blood levels of zinc.²⁰ Although the significance of that finding is not clear, low blood levels of zinc have been associated with an increased risk of complications in both the mother and fetus.²¹

Iron supplementation was associated in one study with an increased incidence of birth defects,²² possibly as a result of an iron-induced deficiency of zinc. Although additional research needs to be done, the evidence suggests that women who are supplementing with iron during pregnancy should also take a multivitamin-mineral formula that contains adequate amounts of zinc. To be on the safe side, pregnant women should discuss their supplement program with a doctor.

Taking vitamin A and iron together has been reported to help overcome iron deficiency more effectively than iron supplements alone.²³ Although the optimal amount of vitamin A needed to help people with iron deficiency has yet to be established, some doctors recommend 10,000 IU per day.

In preliminary research, even a subtle deficiency of iron has been tentatively linked to infertility.²⁴ Women who are infertile should consult a doctor to rule out the possibility of iron deficiency.

Iron requirements increase during pregnancy, making iron deficiency in pregnancy quite common.²⁵ Iron supplement use in the United States is estimated at 85% during pregnancy, with most women taking supplements three or more times per week for three months.²⁶ Pregnant women with a documented iron deficiency need doctor-supervised treatment. In one study, 65% of women who were not given extra iron developed iron deficiency during pregnancy, compared with none who received an iron supplement.²⁷ However, there is a clear increase in reported side effects with increasing supplement amounts of iron, especially iron sulfate.^28,29 Supplementation with large amounts of iron has also been shown to reduce blood levels of zinc.³⁰ Although the significance of that finding is not clear, low blood levels of zinc have been associated with an increased risk of complications in both the mother and fetus.³¹

Iron supplementation was associated in one study with an increased incidence of birth defects,³² possibly as a result of an iron-induced deficiency of zinc. Although additional research needs to be done, the evidence suggests that women who are supplementing with iron during pregnancy should also take a multivitamin-mineral formula that contains adequate amounts of zinc. To be on the safe side, pregnant women should discuss their supplement program with a doctor.

In a study of women in Nepal, where there is a high prevalence of iron and riboflavin deficiencies, supplementation with 30 mg per day of iron and 6 mg per day of riboflavin for six weeks enhanced the effectiveness of vitamin A in the treatment of night blindness.³⁵ It is not known whether these nutrients would be helpful for night blindness in people who are not deficient.

In a preliminary report, two people with a hereditary form of Alzheimer’s disease received daily: coenzyme Q10 (60 mg), iron (150 mg of sodium ferrous citrate), and vitamin B6 (180 mg). Mental status improved in both patients, and one became almost normal after six months.³⁶

Several preliminary studies,^37,38,39,40 though not all,⁴¹ have found a surprisingly high incidence of iron and B vitamin deficiency among people with recurrent canker sores. Treating these deficiencies has been reported in preliminary^42,43 and controlled⁴⁴ studies to reduce or eliminate canker sore recurrences in most cases. Supplementing daily with B vitamins—300 mg vitamin B1, 20 mg vitamin B2, and 150 mg vitamin B6—has been reported to provide some people with relief.⁴⁵ Thiamine (B1) deficiency specifically has been linked to an increased risk of canker sores.⁴⁶ The right supplemental level of iron requires diagnosis of an iron deficiency by a healthcare professional using lab tests.

Iron is important for an athlete because it is a component of hemoglobin, which transports oxygen to muscle cells. Some athletes, especially women, do not get enough iron in their diet. In addition, for reasons that are unclear, endurance athletes, such as marathon runners, frequently have low body-iron levels.^47,48,49 However, anemia in athletes is often not due to iron deficiency and may be a normal adaptation to the stress of exercise.⁴⁹ Supplementing with iron is usually unwise unless a deficiency has been diagnosed. People who experience undue fatigue (an early warning sign of iron deficiency) should have their iron status evaluated by a doctor. Athletes who are found to be iron deficient by a physician are typically given 100 mg per day until blood tests indicate they are no longer deficient. Supplementing iron-deficient athletes with 100 to 200 mg per day of iron increased aerobic exercise performance in some,^51,52,53 though not all,^54,55 double-blind studies. A recent double-blind trial found that iron-deficient women who took 20 mg per day of iron for six weeks were able to perform knee strength exercises for a longer time without muscle fatigue compared with those taking a placebo.⁵⁶

Iron is important for an athlete because it is a component of hemoglobin, which transports oxygen to muscle cells. Some athletes, especially women, do not get enough iron in their diet. In addition, for reasons that are unclear, endurance athletes, such as marathon runners, frequently have low body-iron levels.^56,57,58 However, anemia in athletes is often not due to iron deficiency and may be a normal adaptation to the stress of exercise.⁵⁸ Supplementing with iron is usually unwise unless a deficiency has been diagnosed. People who experience undue fatigue (an early warning sign of iron deficiency) should have their iron status evaluated by a doctor. Athletes who are found to be iron deficient by a physician are typically given 100 mg per day until blood tests indicate they are no longer deficient. Supplementing iron-deficient athletes with 100 to 200 mg per day of iron increased aerobic exercise performance in some,^60,61,62 though not all,^63,64 double-blind studies. A recent double-blind trial found that iron-deficient women who took 20 mg per day of iron for six weeks were able to perform knee strength exercises for a longer time without muscle fatigue compared with those taking a placebo.⁶⁵

The malabsorption that occurs in celiac disease can lead to multiple nutritional deficiencies. The most common nutritional problems in people with celiac disease include deficiencies of essential fatty acids, iron, vitamin D, vitamin K, calcium, magnesium, and folic acid.⁶⁵Zinc malabsorption also occurs frequently in celiac disease⁶⁶ and may result in zinc deficiency, even in people who are otherwise in remission.⁶⁷ People with newly diagnosed celiac disease should be assessed for nutritional deficiencies by a doctor. Celiac patients who have not yet completely recovered should supplement with a high-potency multivitamin-mineral. Some patients may require even higher amounts of some of these vitamins and minerals—an issue that should be discussed with their healthcare practitioner. Evidence of a nutrient deficiency in a celiac patient is a clear indication for supplementation with that nutrient.

After commencement of a gluten-free diet, overall nutritional status gradually improves. However, deficiencies of some nutrients may persist, even in people who are strictly avoiding gluten. For example, magnesium deficiency was found in 8 of 23 adults with celiac disease who had been following a gluten-free diet and were symptom-free. When these adults were supplemented with magnesium for two years, their bone mineral density increased significantly.⁶⁸

Caution: People should not supplement with iron unless diagnosed with iron deficiency, because taking iron when it isn’t needed has no benefit and may be harmful.

Before iron deficiency can be treated, it must be diagnosed and the cause must be found by a doctor. In addition to addressing the cause (e.g., avoiding aspirin, treating a bleeding ulcer, etc.), supplementation with iron is the primary way to resolve iron-deficiency anemia.

If a doctor diagnoses iron deficiency, iron supplementation is essential. Though some doctors use higher amounts, a common daily dose for adults is 100 mg per day. Even though symptoms of deficiency should disappear much sooner, iron deficient people usually need to keep supplementing with iron for six months to one year until the ferritin test is completely normal. Even after taking enough iron to overcome the deficiency, some people with recurrent iron deficiency—particularly some premenopausal women—need to continue to supplement with smaller levels of iron, such as the 18 mg present in most multivitamin-mineral supplements. This need for continual iron supplementation even after deficiency has been overcome should be determined by a doctor.

Since blood is rich in iron, excessive blood loss can lead to iron depletion. Iron deficiency can be identified with simple blood tests. If an iron deficiency is diagnosed, many doctors recommend 100–200 mg of iron per day, although recommendations vary widely.

The relationship between iron deficiency and menorrhagia is complicated. Not only can the condition lead to iron deficiency, but iron deficiency can lead to or aggravate menorrhagia by reducing the capacity of the uterus to stop the bleeding. Supplementing with iron decreases excess menstrual blood loss in iron-deficient women who have no other underlying cause for their condition.^69,70 However, iron supplements should be taken only by people who have, or are at risk of developing, iron deficiency.

Taking vitamin A and iron together has been reported to help overcome iron deficiency more effectively than iron supplements alone.⁷¹ Although the optimal amount of vitamin A needed to help people with iron deficiency has yet to be established, some doctors recommend 10,000 IU per day.

Mild iron deficiency is common, even in people who are not anemic. When iron deficiency is the cause of RLS, supplementation with iron has been reported to reduce the severity of the symptoms.⁷² In one trial, 74 mg of iron taken three times a day for two months, reduced symptoms in people with RLS.⁷³ In people who are not deficient in iron, iron supplementation has been reported to not help reduce symptoms of RLS.⁷⁴ Most people are not iron deficient, and taking too much can lead to adverse effects. Therefore, iron supplements should only be taken by people who have a diagnosed deficiency.

Iron status, as measured by the serum ferritin concentration, was significantly lower in a group of children with ADHD than in healthy children. Ferritin levels were below normal in 84% of the children with ADHD, compared with 18% of the healthy children.⁷⁵ Since iron deficiency can adversely affect mood and cognitive function, iron status should be assessed in children with ADHD, and those who are deficient should receive an iron supplement. In a case report, a young boy with both ADHD and iron deficiency showed considerable improvement in behavior after receiving an iron supplement.⁷⁶ Iron supplementation was also beneficial in a double-blind study of children with ADHD and iron deficiency.⁷⁶

In a study of women in Nepal, where there is a high prevalence of iron and riboflavin deficiencies, supplementation with 30 mg per day of iron and 6 mg per day of riboflavin for six weeks enhanced the effectiveness of vitamin A in the treatment of night blindness.⁷⁷ It is not known whether these nutrients would be helpful for night blindness in people who are not deficient.

Iron deficiency is known to affect mood and can exacerbate depression, but it can only be diagnosed and treated by a doctor. While iron deficiency is easy to fix with iron supplements, people who have not been diagnosed with iron deficiency should not supplement iron.