Patient’s Guide to Oral Iron Supplements


If you are diagnosed with iron deficiency anemia, your doctor may recommend that you increase your iron intake. Eating an iron-rich diet and taking a multivitamin with iron may be a useful way to prevent iron deficiency anemia, but it is usually not enough to treat anemia once it has developed. Your doctor will probably recommend that you take an iron supplement. The goal of this anemia treatment is to eliminate any symptoms you may be experiencing and boost your levels of stored iron and hemoglobin.

Doctor William Ershler, a hematologist at the National Institutes of Health, believes that it is extremely important for you and your doctor to determine why you have iron deficiency anemia as well as treat the symptoms. Iron deficiency anemia may be an early sign of another disease. Finding the cause of your anemia may identify a potentially serious disease before it gets worse. While poor iron absorption from one’s diet or insufficient dietary iron can be a cause of iron deficiency and iron deficiency anemia, increased loss of iron from bleeding such as menstrual bleeding or unidentified bleeding from the stomach, colon or kidneys may be the cause of iron deficiency. If so, it is important that this be identified and treated.

If your doctor wants you to take an iron supplement, you and your doctor will need to find the supplement that is best for you. Iron supplements usually do not need a prescription and are commonly sold in drug stores and supermarkets. There are many iron preparations available with different amounts of iron, different iron salts, complexes, combinations, and dosing regimens. After reading about the different types of iron, browse the shelves of your local drugstore to see all the iron products available to you. However, certain types of iron supplements are less likely to cause gastrointestinal side effects.

What is Iron?

Iron is one of the minerals in the human body. It is one of the components of hemoglobin, the substance in red blood cells that helps blood carry oxygen throughout the body. If you do not have enough iron, your body cannot make hemoglobin, and you may develop anemia, a disorder that occurs when there is not enough hemoglobin in the blood. When you develop anemia, you are said to be “anemic.”

Iron Deficiency Anemia

This type of anemia is called iron-deficiency anemia and is the most common type. Anyone can develop iron-deficiency anemia, although the following groups have a higher risk:

  • Women, because of blood loss during menstrual periods and childbirth
  • Women who are pregnant due to an increase in the body’s need for iron
  • People over 65 who are more likely to have diets that are low in iron
  • People who are on blood thinners such as aspiring, Plavix®, Coumadin®, or heparin
  • People who have kidney failure (especially with dialysis), because they have trouble making red blood cells
  • People who have trouble absorbing iron                                                                                                    

What is Oral Iron Supplementation?

Oral iron supplementation is taking iron by your mouth. There are many different types of oral iron supplements, including pills, capsules, drops, and extended-release tablets. The purpose of oral iron supplementation is to treat your symptoms by increasing the levels of iron and hemoglobin in your body.

You don’t need a prescription to buy iron supplements. Working with your healthcare provider, you can choose which type is best for you. The iron in your body is called “elemental iron.” Oral iron supplements contain different amounts of elemental iron. When you choose a supplement, be sure to check the label to see how much elemental iron it contains; a greater amount means that more iron will be absorbed by your body.

How Much Oral Iron Supplement Do I Need?

Your healthcare provider will tell you how much iron you need to take every day. Typically, adults need to get between 60 and 120 mg of iron a day. Newer research suggests that every other day dosing of iron is just as effective and is better absorbed. Talk to your healthcare provider about what is the best dosing for you. Some examples of commonly recommended iron products and doses may be:

Ferric maltol

30 mg tablet contains 30 mg elemental iron

Ferrous fumarate

324 or 325 mg tablet (contains 106 mg elemental iron per tablet)

Ferrous gluconate

240 mg tablet (contains 27 mg elemental iron per tablet)

324 mg tablet (contains 38 mg elemental iron per tablet)

325 mg tablet (contains 36 mg elemental iron per tablet)

Ferrous sulfate

325 mg tablet (contains 65 mg elemental iron per tablet)

220 mg/5 mL oral elixir (contains 44 mg elemental iron per 5 mL)

75 mg/mL oral solution (contains 15 mg elemental iron per mL)

Polysaccharide iron complex

Various over-the-counter tablets (eg, NovaFerrum 50

50 mg elemental iron per tablet)

15 mg/mL oral solution (contains 15 mg elemental iron per mL)

The best way to take the supplement so that you absorb the greatest amount of iron is to take the supplements every other day. Please note the following:

  • Iron tablets usually should not be taken with food. Milk, caffeine, antacids, calcium supplements and certain antibiotics can decrease the amount of iron that is absorbed.
    • Iron should be taken one hour before or two hours after these items. If you take antacids, your iron tablets should be taken two hours before or four hours after the antacids.
  • Iron tablets are best absorbed in an acidic environment. Try to take your iron supplement with vitamin C, such as a glass of orange juice or with one 250 mg vitamin C tablet to increase absorption.

When Will I Feel Better?

When you should start to feel better depends on your own health situation. Normally, it may take from a few weeks to a few months (after you start your iron supplement) before you start to feel better. Continue to watch your symptoms and take note of side effects that might be caused by the supplements. If you have any questions or concerns, talk to your health care provider.

What Are the Side Effects of Oral Iron?

Oral iron supplements can cause the following side effects:

  • Dark stools
  • Upset stomach
  • Constipation (you may need to take a stool softener)
  • Heartburn

If you start with one iron supplement and find that it causes stomach upset or constipation, do not stop taking iron.  Switch to a different formulation.  You should ask the Pharmacist to assist you to find the iron supplement of your choice since some of the products are kept behind the counter. If you find you cannot tolerate any of the iron supplements, please contact your healthcare provider.

Dr. Ershler states, “Some patients will not be able to take an oral iron supplement, no matter how hard they try.” If you are one of these patients who cannot take an iron supplement by mouth, contact your doctor after no more than a week; side effects are unlikely to get better. Your doctor may recommend an iron injection (intravenous iron). Iron injections are a safe and effective alternative when oral iron does not work or cannot be tolerated, or where there is a need to fully replace iron as quickly as possible because of symptoms or an upcoming surgery.

How Long Will I Have to Take an Oral Iron Supplement?

Your health care provider will let you know how long you will have to take the iron supplement. Usually, after your hemoglobin and iron levels are back to normal, you will continue to take the iron supplement for another six months. Afterward, you will have regular blood tests to measure your iron.


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  3. Centers for Disease Control and Prevention. CDC Recommendations to prevent and control iron deficiency in the United States. MMWR Recomm Rep1998;47:1-29.

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