Iron Dosage Guide
Recommended daily intake by age and gender — based on NIH Dietary Reference Intakes.
Our assessment
Based on FDA adverse event data, iron supplements have a well-documented safety profile with specific risks that increase significantly at high doses. The most important finding is that iron toxicity is dose-dependent, with serious effects occurring primarily at extremely high doses in the hundreds or thousands of mg, which can cause organ failure and coma FDA FAERS ↗.
Safety profile
FDA data reports that taking high doses of iron supplements, especially on an empty stomach, can cause an upset stomach, constipation, nausea, abdominal pain, vomiting, and diarrhea. More serious effects include inflammation of the stomach lining and ulcers. Large amounts of iron can also decrease zinc absorption FDA FAERS ↗. Extremely high doses of iron (in the hundreds or thousands of mg) can cause organ failure, coma, and other severe outcomes FDA FAERS ↗.
How it works
Iron is a mineral that is essential for making hemoglobin, a protein in red blood cells that carries oxygen from the lungs to all parts of the body NIH ODS ↗. Think of iron as a critical component in your body's oxygen delivery system — without adequate iron, your cells cannot function properly NIH ODS ↗.
Our recommendation
Individuals taking proton pump inhibitors, antacids, tetracycline antibiotics, or levothyroxine should be cautious as iron supplements can interact with these medications FDA FAERS ↗. Iron absorption is reduced by calcium and enhanced by vitamin C FDA FAERS ↗. Do not exceed recommended doses, as high doses can cause gastrointestinal distress and more serious effects including stomach inflammation and ulcers FDA FAERS ↗. If you experience severe abdominal pain, vomiting blood, or signs of overdose, seek immediate medical attention FDA FAERS ↗.
AI-assisted analysis. Data sourced from NIH ODS.
Understanding RDAs
Dietary Reference Intakes (DRIs) are a set of reference values used to plan and assess nutrient intakes of healthy people. They include:
- RDA (Recommended Dietary Allowance) — The average daily intake sufficient to meet the nutrient requirements of nearly all (97-98%) healthy individuals.
- AI (Adequate Intake) — Established when evidence is insufficient to develop an RDA. Based on observed nutrient intake by healthy people.
- UL (Tolerable Upper Intake Level) — The maximum daily intake unlikely to cause adverse health effects. Exceeding the UL increases the risk of toxicity.
Values vary by age, gender, and life stage (pregnancy, lactation).
Source: National Academies of Sciences, Engineering, and Medicine
Recommended Dietary Allowance
| Age | Male | Female | Pregnant | Lactating |
|---|---|---|---|---|
| 0-6 months* | 0.27 mg | 0.27 mg | ||
| 7-12 months* | 11 mg | 11 mg | ||
| 1-3 years | 7 mg | 7 mg | ||
| 4-8 years | 10 mg | 10 mg | ||
| 9-13 years | 8 mg | 8 mg | ||
| 14-18 years | 11 mg | 15 mg | 27 mg | 10 mg |
| 19-50 years | 8 mg | 18 mg | 27 mg | 9 mg |
| 51+ years | 8 mg | 8 mg |
Source: National Academies of Sciences, Engineering, and Medicine
Deficiency
Iron deficiency can cause anemia, fatigue, weakness, pale skin, and shortness of breath. Groups at risk include pregnant women, infants, young children, women with heavy menstrual periods, and people with certain medical conditions.