Iron poisoning is a potentially fatal pediatric emergency, with severity directly related to the amount of elemental iron ingested.
Adult iron preparations and prenatal vitamins are the most toxic sources, whereas children’s vitamins, multivitamin preparations, and nonionic forms (carbonyl iron, iron polysaccharide) rarely contain enough elemental iron to cause significant toxicity.
Iron Toxicity Based on Ingested Dose
The risk assessment and severity of iron toxicity are determined strictly by the amount of elemental iron ingested, rather than the total weight of the iron salt tablet.
The therapeutic dose for treating iron deficiency anemia is typically 3 to 6 mg/kg/day.
Acute ingestions exceeding these therapeutic limits are categorized based on the milligram per kilogram (mg/kg) of elemental iron ingested, which correlates with expected clinical manifestations.
Dose of Elemental Iron Ingested
Expected Toxicity and Clinical Features
<20 mg/kg
Asymptomatic / Non-toxic: Individuals typically do not exhibit any symptoms and require no specific treatment.
20−60 mg/kg
Mild to Moderate Toxicity: Results primarily in local gastrointestinal (GI) symptoms such as abdominal pain, vomiting, and diarrhea.
60−120 mg/kg
Severe Toxicity: High potential for systemic toxicity, including metabolic acidosis, shock, coagulopathy, and hepatorenal failure.
>120 mg/kg
Potentially Lethal: Associated with life-threatening systemic collapse, severe morbidity, and high mortality.
Iron has a direct corrosive effect on the gastrointestinal mucosa, leading to hematemesis, melena, ulceration, and potential perforation.
The presence of free iron causes massive volume losses, increased capillary membrane permeability, and vasodilation, which collectively precipitate early hypotension.
Iron accumulates in target tissues, notably the Kupffer cells of the liver and myocardial cells, causing hepatotoxicity, coagulopathy, and cardiac dysfunction.
Profound metabolic acidosis occurs due to a combination of hypovolemia, hypotension, and iron’s direct interference with oxidative phosphorylation and the Krebs cycle.
Iron Salt / Preparation
Percentage of Elemental Iron
Calculation Rule
Ferrous Fumarate
33%
Divide total salt dose by 3
Ferrous Sulfate (dried)
≈30%
Divide total salt dose by 3.3
Ferrous Sulfate (heptahydrate)
20%
Divide total salt dose by 5
Ferrous Gluconate
12%
Divide total salt dose by 9
Ferric Chloride
≈28.5%
Divide total salt dose by 3.5
Ferrous Chloride
25%
Divide total salt dose by 4
Clinical Manifestations
The clinical progression of acute iron toxicity is classically described in five overlapping stages.
Patients who remain completely asymptomatic without gastrointestinal symptoms within 6 hours of ingestion are highly unlikely to develop serious toxicity.
Phase
Time After Ingestion
Characteristic Clinical Features
1. Gastrointestinal
6 hours
Vomiting, diarrhea, hematemesis, hematochezia.
2. Latent
6−24 hours
Resolution of gastrointestinal symptoms, tachycardia, acidosis, depressed mental status.
3. Systemic
12−24 hours
Return of gastrointestinal symptoms, severe acidosis (HAGMA), leukocytosis, coagulopathy, renal failure, lethargy or coma, and cardiovascular collapse.
4. Hepatic
2−5 days
Fulminant liver failure, coagulopathy.
5. Obstructive
3−6 weeks
Pyloric or bowel scarring leading to obstruction.
Diagnostic and Laboratory Evaluation
Serum iron levels should be drawn 4−6 hours post-ingestion in symptomatic patients or those with a history of a massive exposure.
A serum iron concentration <350μg/dL at 4−8 hours suggests a low risk for significant toxicity.
A serum iron concentration of 350−500μg/dL indicates moderate toxicity.
A serum iron concentration >500μg/dL signifies that significant, life-threatening toxicity is likely.
Routine laboratory evaluation must include an arterial or venous blood gas, lactate, complete blood count, serum glucose, liver transaminases, and coagulation parameters.
Iron poisoning classically presents with an elevated anion gap metabolic acidosis (part of the MUDPILES mnemonic).
An abdominal radiograph (KUB) should be obtained as it may reveal radiopaque iron tablets (part of the CHIPPED mnemonic), although the absence of radiopacities does not rule out iron ingestion.
Emergency Management
Gastrointestinal Decontamination
Activated charcoal does not bind to elemental iron and is entirely ineffective for gastrointestinal decontamination in this setting.
Whole-bowel irrigation (WBI) is the definitive decontamination strategy of choice for iron ingestion, serving to mechanically flush unabsorbed iron pills from the gastrointestinal tract.
Hemofiltration may be considered as an adjunctive method to remove iron from the systemic circulation.
Antidotal Therapy
Deferoxamine is the specific chelating antidote utilized for moderate to severe iron intoxication.
The deferoxamine-iron complex is excreted in the urine, classically imparting a reddish (“vin rosé”) discoloration, though the intensity of this color should not be used to guide or terminate therapy.
Therapy is maintained until clinical symptoms resolve and the metabolic acidosis is fully corrected.
Antidote Parameter
Guidelines for Deferoxamine Administration
Indications
Serum iron concentration >500μg/dL OR the presence of moderate to severe symptoms (e.g., metabolic acidosis, lethargy) regardless of the serum iron level.
