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Iron Intake, Supplements & Ways to Increase/Decrease

Written by Maja Stanojevic, MD | Last updated:
Nattha Wannissorn
Puya Yazdi
Medically reviewed by
Nattha Wannissorn, PhD, Puya Yazdi, MD | Written by Maja Stanojevic, MD | Last updated:

Factors that prevent or enhance iron absorption can have a big impact on iron levels, regardless of dietary intake or supplementation. Read this post to learn about these factors. We will also discuss iron supplements and ways to increase or decrease iron levels.

Sources of Iron

Iron-rich foods include [1, 2]:

  • meat and poultry, including organ meats like liver, heart, kidney, and blood
  • fish, including shellfish and sardines

Plant-based foods that are high in iron in the non-heme form (but may also be high in substances that prevent iron absorption) include:

  • pulses, including chickpeas, beans, peas, and lentils
  • seeds, including sesame and pumpkin seeds
  • green leafy vegetables, including broccoli and kale

Some (not necessarily healthy) foods are fortified with iron. These include flour, grains, cereals, pasta, rice, bakery products, milk and dairy products, chocolate drinks, and infant formulas [3, 4].

A number of iron supplements are available in the form of ferrous sulfate, ferrous gluconate, ferrous fumarate, and heme iron. They are indicated for the prevention and treatment of iron deficiency and iron deficiency anemia [5, 1].

Adequate Iron Intake

Adults require at least 8 mg of iron per day [6, 7].

Women of childbearing age (19 – 50 yrs) should get more iron (around) 18 mg/day, because they lose more iron due to menstrual bleeding.

Infants and children 1 to 3 years require 11 and 7 mg/day, respectively, while children aged 4 – 8 and 9 – 13 require at least 10 and 8 mg/day, respectively, in order to prevent developmental delays and behavioral disturbances [6, 7].

Iron Supplementation

If you have iron deficiency anemia, your doctor may prescribe iron therapy [8]. Keep in mind that It may take several months of supplementation to correct iron deficiency.

In many populations, the amount of iron absorbed from the diet is not enough to meet most individual requirements, especially during infancy, intense exercise, and pregnancy, where biological iron needs are the highest [9, 10].

If the amount of absorbable iron in the diet cannot be readily improved, iron supplementation is required to prevent iron deficiency anemia. This is often the case for children 6-24 months of age and pregnant women [11, 12, 13].

Iron supplements are necessary for the rapid treatment of severe iron deficiency anemia in males and females from all age groups [14].

Different Forms of Iron Supplements

Supplemental iron is found in ferrous (+2) and ferric (+3) forms. Since the ferric form must be converted in the body to the ferrous form for absorption, the ferrous form is more bioavailable and thus preferred [5].

Commonly used oral ferrous iron supplements include [14, 15, 16, 5]:

  • Ferrous citrate
  • Ferrous sulfate
  • Ferrous gluconate
  • Ferrous succinate
  • Amino acid chelates, such as iron bisglycinate and iron aspartate
  • Heme iron

While the most commonly studied iron supplement is ferrous sulfate, food fortification and supplementation studies have shown that amino acid chelate forms of iron (such as glycinate) are better or equally well absorbed [17, 18].

For example, 25 mg of ferrous glycinate was able to bring up iron levels to the same level as did 50 mg of ferrous sulfate in a study with pregnant women [19].

Newer formulations iron supplements like heme iron polypeptides, iron amino acid chelates, carbonyl iron, and sugar-iron complexes may be more tolerable and have fewer GI side effects than ferrous salts. However, some of these preparations are not as bioavailable and their clinical efficacy is yet to be proven [20, 5].

Iron injections require medical supervision. They can be given when oral iron supplementation is not tolerated, which is often the case for people with malabsorption from celiac disease and inflammatory bowel disease [21].

It is also recommended in cases where hemoglobin must be increased rapidly like after a surgery or blood transfusion [22].

Iron injections are more expensive than oral treatments and cannot be taken during the first trimester of pregnancy [21, 14].

Injections of iron carboxymaltose and iron isomaltoside are recommended for their ability to be given in larger doses and good safety profiles [23].

Side Effects

Oral iron causes side effects in up to 60% of people, such as gut irritation, constipation, diarrhea, nausea, and heartburn [24, 16].

To minimize side effects and increase tolerability, lower doses between meals are recommended, although food reduces iron absorption by two-thirds [25, 14].

After injections, severe side effects include allergy, low blood pressure, nausea, and stomach pain [14].


Iron supplements should not be used in people who have:

  • Normal iron balance (men, postmenopausal women) because iron will not be absorbed and will just pass through the body [26].
  • Hemochromatosis (iron overload) [27].
  • Received repeated blood transfusions [28].
  • Hemolytic anemia, which may increase blood iron levels and cause toxicity [28].
  • Inflammation of the digestive system (peptic ulcer, colitis, diverticular disease), because it can directly irritate the gut and exacerbate these conditions [29].
  • Lupus [30, 31].

Drug Interactions

Iron supplements may reduce the absorption and efficacy of the following medications. You should consult your physician or pharmacists to confirm that your supplements can be safely used with the medications that you are using.

  • Levodopa (Sinemet®, Stalevo®), methyldopa (Aldomet®) [32, 33, 34]
  • Levothyroxine (Levothroid®, Levoxyl®, Synthroid®) [35]
  • Penicillamine (Cuprimine®, Depen®) [36, 37]
  • Quinolones [38]
  • Tetracyclines [39]
  • Ciprofloxacin [40]
  • Bisphosphonates [41]
  • Medications that decrease stomach acidity, such as antacids, histamine (H2) receptor antagonists (cimetidine, ranitidine), and proton pump inhibitors (omeprazole, lansoprazole), may impair iron absorption [42, 43].
  • Cholestyramine (Questran®) should be taken at least four hours apart from iron supplements because they may interfere with iron absorption [44].
  • Allopurinol (Zyloprim®) may increase iron storage in the liver and should not be used in combination with iron supplements [45].

Dosage and Recommendations

For treating iron deficiency anemia, a dose of 60-120 mg of elemental iron (amount of actual iron in the supplement) from ferrous sulfate is recommended per day for a minimum of 3 months in adolescents and adults, including pregnant women [46].

Increasing Iron without Iron Supplements

The most important thing is to work with your doctor to find out what’s causing your low iron and to treat any underlying conditions. Dietary and lifestyle changes won’t help if underlying conditions are decreasing your iron levels.

Discuss lifestyle changes listed below with your doctor. None of these strategies should ever be done in place of what your doctor recommends or prescribes!

1) Iron-Rich Foods

Make sure your diet is healthy and well balanced. Increase your intake of foods that are rich in iron to replenish your iron stores. These include red meat, poultry, fish, beans, lentils, tofu, tempeh, nuts, and seeds.

Dietary iron is found in two forms: heme and non-heme [47].

The main sources of heme iron are hemoglobin and myoglobin from red meat, chicken, and fish, whereas non-heme iron is primarily found in cereals, fruits, legumes, and vegetables. Heme iron has high bioavailability (15%-35%) and dietary factors have minimal effects on its absorption, while nonheme iron absorption is much lower (2%-20%) and strongly affected by the presence of other food types [48].

That’s why people on vegetarian and vegan diets need to be mindful of their iron intake.

Most studies in young women have found a positive association between iron status (ferritin and iron), and meat and other heme iron consumption [49, 50, 51, 52, 53].

2) Vitamin C

Absorption from vegetable-based meals may be increased as much as sixfold if the meal is accompanied by large quantities of vitamin C [54, 55].

Vitamin C and citric acid enhance iron uptake in a dose-dependent manner in part by acting as weak chelators to help solubilize iron in the small intestine [56].

A study found that vitamin C intake was positively correlated with iron status in women [51].

Vitamin C also helps with iron absorption in the presence of substances that inhibit iron absorption, including phytates, polyphenols, calcium and proteins [57, 58, 59].

3) Vitamin A

Phytates found in whole grains and legumes decrease iron absorption. When you eat them, add foods rich in vitamin A and beta-carotene – research shows that they can increase iron absorption and can override the influence of phytates [60, 61, 62].

Foods rich in vitamin A and beta-carotene include carrots, sweet potatoes, fish, cantaloupe, bell peppers, squash, and grapefruit.

Studies have found that vitamin A (retinol) helps treat iron-deficiency anemia and can improve iron status in children and pregnant women [63, 64].

4) Cast Iron Utensils

An easy way to get more iron in your meals is to use cast iron utensils [65].

5) Alcohol in Moderation

Alcohol intake has positive associations with iron status [49, 52, 51]. Alcohol works by decreasing hepcidin, a liver protein that blocks iron absorption in the gut.

Beer is linked to higher blood ferritin concentrations than wine or spirits [66, 67].

Data from the National Health and Examination Survey in the US (> 8.8k people) concluded that two alcoholic drinks daily may reduce the risk of iron deficiency and iron deficiency anemia in men and women [68].

However, bear in mind that drinking alcohol in excess can have serious adverse side effects, Discuss your alcohol consumption with your doctor.

Ways to Decrease Iron

The most important thing is to work with your doctor to find out what’s causing your high iron and to treat any underlying conditions. The additional lifestyle changes listed below are other things you may want to discuss with your doctor. None of these strategies should ever be done in place of what your doctor recommends or prescribes!

1) Phytates

Phytates decrease iron absorption at very low concentrations of 2–10 mg of phytate per meal [69].

Phytates are “anti-nutrients” found in legumes, whole grains, nuts, and seeds. Phytates can inhibit non-heme iron absorption (up to 50 %) by binding to the iron atom [47].

Soy protein (found in tofu, texturized vegetable proteins, and some processed meat products) can reduce iron absorption because it contains phytates [47].

A study in middle-aged females found that the more white and wholegrain bread, and nut and seed consumption they consumed, the lower the blood ferritin they have [51].

2) Polyphenols or Tannins

Found in coffee, black tea, herbal tea, red wine, and some fruits and vegetables, polyphenolic compounds and tannins can significantly inhibit non-heme iron absorption [70, 71, 72].

Therefore, you can decrease iron absorption by consuming the following beverages within an hour of a meal:

  • Green and black tea [73, 74]
  • Coffee [70]
  • Cocoa [75]
  • Herbal teas, such as chamomile, lime flower, pennyflower, mint, and vervain [71, 76, 77]

3) Calcium

Calcium dose-dependently inhibits both nonheme and heme iron absorption [78, 79].

However, its effects are limited when one consumes a wide variety of foods with varying amounts of enhancers and inhibitors of iron absorption [47].

4) Proteins in Milk and Eggs

While proteins from animal flesh increase iron absorption, proteins from milk and eggs (with the exception of ovalbumin) reduces iron absorption when consumed with a low-iron food [80].

5) Regular Intense Exercise

Daily iron losses are greater in athletes engaged in intense exercise, likely due to growing blood cell mass, muscle mass, and rupture of red blood cells [81].

6) Avoid Alcohol

Alcohol increases iron levels. It works by decreasing hepcidin, a liver protein that blocks iron absorption in the gut [82, 67, 83].

7) Frequent Blood Donation

In more severe cases, your doctor may prescribe blood donation, blood removal (phlebotomy), or drugs that bind and remove iron (chelation) [84].

Blood donors experience lower blood iron levels because each 500 mL of donated blood contains around 200 to 250 mg of iron [85, 86].

Interactions Between Iron and Other Substances

1) Calcium

Calcium decreases iron absorption.

In order to maximize iron absorption, iron supplements should be taken two hours apart from calcium-rich foods (milk, cheese) or calcium supplements [87].

2) Zinc

Zinc deficiency is associated with iron deficiency anemia, and it aggravates its symptoms.

Iron >supplements, taken together with zinc supplements on an empty stomach, may inhibit the absorption of zinc.

When taken with food, supplemental iron does not inhibit zinc absorption [88, 89, 90].

3) Vitamin A

Vitamin A affects iron transport and red blood cell production directly [89].

4) Vitamin C

Vitamin C increases the absorption of non-heme iron in the gut. It also influences the storage and transport of iron in the body [89].

5) Copper

An adequate copper blood level is necessary for normal iron metabolism and red blood cell formation [91].

6) Iodine

Severe iron deficiency anemia can impair iodide metabolism and the production of thyroid hormones. Studies suggest that correcting iron deficiency anemia improves the efficacy of iodine supplementation to treat thyroid diseases [92, 93, 94].

7) Aluminum

Iron depletion increases aluminum absorption. Susceptible individuals, such as renal failure patients, have an increased risk of aluminum toxicity if they are iron deficient [95].

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