| Ferrous Sulfate | Inorganic Salt | ❌ No | ~20% | Moderate | Moderate–Low | Most prescribed globally; may cause constipation/gastric distress |
| Ferrous Fumarate | Inorganic Salt | ❌ No | ~33% | Moderate–High | Moderate | High elemental iron; often used in pregnancy |
| Ferrous Gluconate | Inorganic Salt | ❌ No | ~12% | Moderate | Good | Gentler on stomach; used in pediatric/geriatric formulations |
| Iron Bisglycinate | Amino Acid Chelate | ✅ Yes | ~20% | High | Very Good | Superior absorption and GI tolerance; ideal for sensitive users |
| Iron Glycinate | Amino Acid Chelate | ✅ Yes | ~20% | High | Excellent | Similar to bisglycinate; often used in multivitamin blends |
| Iron Aspartate | Amino Acid Chelate | ✅ Yes | ~18–20% | Moderate–High | Good | Less common; niche premium formulations |
| Iron Orotate | Mineral Chelate | ✅ Yes | ~15–20% | Moderate–High | Good | Marketed as high cell penetration iron; premium but less studied |
| Iron Polysaccharide Complex | Complexed Iron | ⚠️ Semi-Chelated | ~100% | Moderate | Very Good | Non-ionic; gentle release; useful for long-term supplementation |
| Carbonyl Iron | Elemental Iron | ❌ No | ~100% | Slow-release | Very Good | Micro-pure iron particles; safer for children; low reactivity |
| Heme Iron Polypeptide | Organic (Animal-Based) | ✅ Yes | ~11% | Very High | Excellent | From bovine hemoglobin; ideal for meat-deficient individuals |
| Ferric Citrate | Inorganic (Ferric) | ❌ No | ~18% | Moderate | Moderate | Used in CKD to manage phosphate and iron simultaneously |
