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Iron Chews Side Effects

Generic Name: carbonyl iron

Note: This page contains information about the side effects of carbonyl iron. Some of the dosage forms included on this document may not apply to the brand name Iron Chews.

For the Consumer

Applies to carbonyl iron: suspension

Check with your doctor if any of these most COMMON side effects persist or become bothersome:

Constipation; darkened or green stools; diarrhea; loss of appetite; nausea; stomach cramps, pain, or upset; vomiting.

Seek medical attention right away if any of these SEVERE side effects occur while taking carbonyl iron (the active ingredient contained in Iron Chews)

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); black or tarry stools; blood or streaks of blood in the stool; fever; severe or persistent nausea, stomach pain, or vomiting; vomit that looks like blood or coffee grounds.

For Healthcare Professionals

Applies to carbonyl iron: oral suspension, oral tablet, oral tablet chewable


Gastrointestinal side effects have been reported the most frequently. They have included diarrhea (45%) vs. placebo (3%), cramping (38%) vs. placebo (0%), nausea (30%) vs. placebo (8%), constipation (25%) vs. placebo (14%), heartburn (17%) vs. placebo (6%), and epigastric discomfort (16%) vs. placebo (11%).[Ref]

Constipation may be relieved by administering docusate sodium 100 mg to 200 mg per day in addition to increasing the intake of oral fluids, such as water.[Ref]


Iron overload (i.e., hemosiderosis) has been reported in patients genetically predisposed, or have underlying disorders, that augment the absorption of iron. It has also occurred following administration of excessive parenteral iron therapy, combination of oral and parenteral iron, or in patients with hemoglobinopathies that were erroneously diagnosed as iron deficiency anemia. Hemosiderosis is treated with repeated phlebotomy or long-term administration of deferoxamine. The liver is particularly susceptible to toxicity in iron-overload states.

Stained teeth have been reported primarily following ingestion of iron liquid preparations. Liquid dosage forms should be diluted in juice or water and sipped through a straw to aid in prevention of staining.[Ref]

Other side effects have included iron overload (hemosiderosis) and stained teeth. Secondary hemochromatosis due to prolonged iron ingestion has been reported rarely. An unpleasant taste following carbonyl iron ingestion has been reported in 40% to 70% of patients.[Ref]

Nervous system

Nervous system side effects have included headache (29%) vs. placebo (25%), and weakness (11%) vs placebo (9%).[Ref]


1. "Product Information. Feosol Caplets (carbonyl iron)" SmithKline Beecham, Philadelphia, PA.

2. Gordeuk VR, Brittenham GM, Hughes M, Keating LJ, Opplt JJ "High-dose carbonyl iron for iron deficiency anemia: a randomized double-blind trial." Am J Clin Nutr 46 (1987): 1029-34

3. Devasthali SD, Gordeuk VR, Brittenham GM, Bravo JR, Hughes MA, Keating LJ "Bioavailability of carbonyl iron: a randomized, double-blind study." Eur J Haematol 46 (1991): 272-8

4. Gordeuk VR, Brittenham GM, McLaren CE, Hughes MA, Keating LJ "Carbonyl iron therapy for iron deficiency anemia." Blood 67 (1986): 745-52

5. Gordeuk VR, Brittenham GM, Hughes MA, Keating LJ "Carbonyl iron for short-term supplementation in female blood donors." Transfusion 27 (1987): 80-5

Not all side effects for Iron Chews may be reported. You should always consult a doctor or healthcare professional for medical advice. Side effects can be reported to the FDA here.

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