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.^{7 , 8} However, iron supplements should be taken only by people who have, or are at risk of developing, iron deficiency.

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.

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.

Liver extracts from beef are a rich natural source of many vitamins and minerals, including iron. Bovine liver extracts provide the most absorbable form of iron—heme iron—as well as other nutrients critical in building blood, including vitamin B12 and folic acid . Liver extracts can contain as much as 3–4 mg of heme iron per gram.

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. In one trial, 74 mg of iron taken three times a day for two months, reduced symptoms in people with RLS.⁹ In people who are not deficient in iron, iron supplementation has been reported to not help reduce symptoms of RLS.¹⁰ 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.¹¹ 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.¹² Iron supplementation was also beneficial in a double-blind study of children with ADHD and iron deficiency.¹³

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.^{14 , 15 , 16} However, anemia in athletes is often not due to iron deficiency and may be a normal adaptation to the stress of exercise.¹⁷ 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,^{18 , 19 , 20} though not all,^{21 , 22} 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.²³

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.

Several preliminary studies,^{24 , 25 , 26 , 27} though not all,²⁸ 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^{29 , 30} and controlled³¹ 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.³² Thiamine (B1) deficiency specifically has been linked to an increased risk of canker sores.³³ The right supplemental level of iron requires diagnosis of an iron deficiency by a healthcare professional using lab tests.

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 .³⁴ Zinc malabsorption also occurs frequently in celiac disease³⁵ and may result in zinc deficiency, even in people who are otherwise in remission.³⁶ 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.³⁷

Taurine has been shown, in a double-blind study, to improve the response to iron therapy in young women with iron-deficiency anemia.³⁸ The amount of taurine used was 1,000 mg per day for 20 weeks, given in addition to iron therapy, but at a different time of the day. The mechanism by which taurine improves iron utilization is not known.

Taking vitamin A and iron together has been reported to help overcome iron deficiency more effectively than iron supplements alone.³⁹ 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.

Caution: People who are not diagnosed with iron deficiency should not supplement with iron. Taking iron when it isn’t needed has no benefit and may do some harm.

Vitamin C increases the absorption of non-heme iron.⁴⁰ Some doctors advise iron-deficient people to take vitamin C (typically 100–500 mg) at the same time as their iron supplement.⁴¹

A high degree of association between iron-deficiency anemia and vitamin D deficiency in Asian children has been previously reported.⁴² In three different ethnic groups living in England, iron-deficiency anemia was found to be a significant risk factor for low vitamin D levels in children.⁴³ These findings suggest that children with iron-deficiency anemia should be screened for vitamin D deficiency and be given vitamin D supplements if necessary.

People with DH frequently have mild malabsorption (difficulty absorbing certain nutrients) associated with low stomach acid (hypochlorhydria) and inflammation of the stomach lining (atrophic gastritis).⁴⁴ Mild malabsorption may result in anemia ⁴⁵ and nutritional deficiencies of iron , folic acid ,^{46 , 47} vitamin B12 ,^{48 , 49} and zinc .^{50 , 51 , 52} More severe malabsorption may result in loss of bone mass.⁵³ Additional subtle deficiencies of vitamins and minerals are possible, but have not been investigated. Therefore, some doctors recommend people with DH have their nutritional status checked regularly with laboratory studies. These doctors may also recommend multivitamin-mineral supplements and, to correct the low stomach acid, supplemental betaine HCl (a source of hydrochloric acid).

In preliminary research, even a subtle deficiency of iron has been tentatively linked to infertility.⁵⁴ Women who are infertile should consult a doctor to rule out the possibility of iron deficiency.