What Is Iron Carbonyl? Uses, Dosage, and What You Need to Know in 2026

Iron Carbonyl — also called carbonyl iron — is an oral iron supplement used to treat and prevent iron deficiency and iron deficiency anemia (IDA). It's available over the counter without a prescription, primarily under the brand name Feosol Natural Release, as well as Icar, Ferra-Cap, Wee Care, and others.

This guide covers everything you need to know about Iron Carbonyl in 2026 — what it is, who needs it, how to take it, and how it compares to other iron supplements.

What Is Carbonyl Iron?

Carbonyl iron is a form of elemental iron — meaning it is uncharged iron metal, not an iron salt like ferrous sulfate or ferrous gluconate. It is made through a manufacturing process in which iron pentacarbonyl vapor is thermally decomposed, producing submicroscopic spheres of highly pure elemental iron. The word "carbonyl" refers to the manufacturing method, not to the composition of the iron itself.

Unlike ionic iron salts (ferrous sulfate, ferrous gluconate, ferrous fumarate), carbonyl iron must be converted from its elemental form to ferrous iron (Fe2+) by the acid in your stomach before your body can absorb it. This slow conversion is what gives carbonyl iron its distinctive safety profile.

What Is Iron Carbonyl Used For?

Iron Carbonyl is used to:

• Treat iron deficiency anemia (IDA): Iron deficiency anemia occurs when your body doesn't have enough iron to produce hemoglobin — the protein that carries oxygen in red blood cells. Iron Carbonyl replenishes iron stores and supports new red blood cell production.
• Prevent iron deficiency: Used prophylactically for people at high risk of iron deficiency — including pregnant women, premature infants, frequent blood donors, and women with heavy menstrual periods.
• Support dietary iron supplementation: For people whose diet is deficient in iron-rich foods (vegetarians, vegans, and people with restricted diets).

Who Should Take Iron Carbonyl?

Iron Carbonyl is appropriate for:

• Adults and children with confirmed iron deficiency (diagnosed by blood test)
• Pregnant women who need iron supplementation during pregnancy
• Households with young children where accidental ingestion safety is a priority
• Patients who've had GI side effects (nausea, constipation) with ferrous sulfate

Iron Carbonyl is generally NOT recommended for people with hemochromatosis (iron overload disorder), hemosiderosis, or those with normal iron levels. Always confirm iron deficiency with a blood test before starting supplementation.

Iron Carbonyl Dosage: How Much Should I Take?

Standard dosing for Iron Carbonyl:

• Adults (treatment): 45–90 mg elemental iron per day. One to two 45 mg tablets daily (e.g., one Feosol Natural Release caplet once or twice daily).
• Adults (prevention): Lower doses as directed by a physician.
• Children (prophylaxis): 1–2 mg elemental iron/kg/day, maximum 15 mg/day, in 1–2 divided doses.
• Children (IDA treatment): 3–6 mg elemental iron/kg/day divided every 8–12 hours.
• Duration: Do not take for more than 6 months without a doctor's advice, unless directed for ongoing conditions like menorrhagia or continuous blood loss.

Available Dosage Forms for Iron Carbonyl

Iron Carbonyl is available in several forms to accommodate different patient needs:

• 45 mg tablet (Feosol Natural Release): Most common adult form. Swallow whole with water.
• 15 mg chewable tablet (Iron Chews): For patients who have difficulty swallowing tablets.
• Oral suspension (15 mg/1.25 mL — Wee Care): Liquid form for infants and young children. Shake well before measuring dose.
• Combination with vitamin C (Icar-C, Vitron-C): Vitamin C (ascorbic acid) enhances iron absorption. Combination products provide both in a single tablet.

How to Take Iron Carbonyl for Best Results

To get the most out of Iron Carbonyl:

• Take it on an empty stomach (1 hour before or 2 hours after meals) for best absorption. If it upsets your stomach, take it with a small amount of food.
• Take it with a full 8 oz glass of water or orange juice (vitamin C in OJ enhances absorption).
• Avoid taking with antacids, milk, dairy products, tea, or coffee — these reduce iron absorption.
• Separate from tetracycline or fluoroquinolone antibiotics by at least 2–6 hours.
• Separate from levothyroxine (thyroid medication) by at least 4 hours.

For a full list of Iron Carbonyl side effects and what to watch for, see our Iron Carbonyl side effects guide.