| 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 |
