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A Patients Guide to Oral Iron Supplements

November 14, 2008
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.

Dr. William Ershler, MD, a hematologist at the National Institutes of Health, feels 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 catch a potentially serious disease before it gets worse.

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 a large number of 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.

Ferrous Iron Types and Sizes
Iron Supplement Tablet Size Elemental Iron
Ferrous fumarate 325 mg 108 mg
Ferrous sulfate 325 mg 65 mg
Ferrous gluconate 325 mg 35 mg

Fishbane S, et al. Kidney Int Suppl. 1999 Mar.4

Types of Iron Supplements

There are two general types of iron supplements which contain either the ferrous or ferric form of iron. Ferrous iron is the best absorbed form of iron supplements. Most available iron pills contain ferrous iron. There are three types of ferrous iron supplements commonly found: ferrous sulfate, ferrous fumarate, and ferrous gluconate. While all three come in a 325 mg tablet size, each one contains a different amount of the form of iron used by your body, called elemental iron. When choosing an iron supplement, it is important to remember to look at the amount elemental iron in each tablet, instead of the size of the tablet.[1]

Adults will usually require a dose of 60-200 mg of elemental iron daily, depending on the severity of the anemia. [SIZE=4]Since the amount of iron absorbed decreases as doses get larger, most people should take their daily iron supplement in two or three equally spaced doses. For adults who are not pregnant, the Centers for Disease Control and Prevention (CDC) generally recommends taking 50-60 mg of oral elemental iron (the approximate amount of elemental iron in one 325 mg tablet of ferrous sulfate) 2 twice daily for three months for the treatment of iron deficiency anemia.3 [/SIZE]However, your doctor will individually evaluate your condition and prescribe the amount of iron you need.

Iron supplements are available in regular tablets and capsules, liquid, drops, and coated or extended release tablets and capsules. Regular tablets and capsules are the best absorbed iron pill and are usually the most economical. Liquid and drop iron supplements are necessary for young children and people with problems swallowing pills, but may temporarily stain your teeth. Iron from coated or delayed-release preparations may have fewer side effects, but are not as well absorbed and not usually recommended. If your doctor recommends an iron supplement, consider the type of iron and pill, as well as the cost.

Controlling the Side Effects
All iron supplements will cause your stool to become dark in color, but some people may also experience side effects which make it hard to follow recommended dosages. An upset stomach and constipation are the most common side effects of iron. If iron makes you constipated, consider taking a stool softener. Here are some tips to help you take your iron more comfortably and effectively.

When to Use Each Oral Iron Type
Pill Type Recommendation
Regular tablets and capsules Best absorbed; most economical type
Liquid or drops For young children or those having trouble swallowing pills; may stain your teeth
Coated or extended release tablets and capsules Fewer side effects but not absorbed as well

NIH. ODS Iron Fact Sheet.4

  • Iron supplements can upset your stomach. Starting with half the recommended dose and gradually increasing to the full dose will help minimize these side effects.
  • Iron supplements are absorbed better if taken an hour before meals. However your doctor may tell you to take your iron with food to reduce an upset stomach.
  • If iron makes you constipated, consider taking a stool softener such as docusate sodium along with your iron. Many products are available with this ingredient. Your pharmacist can help you choose the product that is best for you.
  • Milk, caffeine, antacids and calcium supplements can decrease iron absorption and should not be taken at the same time as iron supplements.
  • You can get the most benefit from iron pills if you take them with vitamin C or drink orange juice. Vitamin C increases the absorption of iron.1


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, your doctor may recommend an iron injection. Iron injections are a safe and effective alternative when iron tablets do not work or cannot be tolerated. Read more about this form of iron supplement to find out if Iron Injections Are Right for You?

If you think you have anemia, please contact your doctor. Do not try to treat yourself or take iron pills without talking to your doctor. Taking too much iron over a period of time can be dangerous. It is important to keep iron pills out of the reach of children.

    1. National Institute of Health. Office of Dietary Supplements. Dietary Supplement Fact Sheet: Iron. Link.


    1. Medline Plus. Drugs and Supplements: Iron Link.


    1. Centers for Disease Control and Prevention. CDC Recommendations to prevent and control iron deficiency in the United States. MMWR Recomm Rep 1998;47:1-29. Link.


    1. Fishbane S, Mittal SK, Maesaka JK. Beneficial effects of iron therapy in renal failure patients on hemodialysis. Kidney Int Suppl. 1999 Mar;69:S67-70. Link.


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