Comparison of Iron Supplement Forms by Elemental Iron Content
| Iron Compound | Typical Elemental Iron % | Elemental Iron per 325 mg tablet | Notes |
|---|---|---|---|
| Ferrous sulfate | ~20% | ~65 mg | Most commonly prescribed; inexpensive; moderate GI side effects |
| Ferrous gluconate | ~12% | ~38 mg | Gentler on the stomach but lower iron content |
| Ferrous fumarate | ~33% | ~106 mg | High elemental iron per dose; more likely to cause constipation |
| Iron polysaccharide | ~100% | ~150 mg per 150 mg capsule/tablet | Non-ionic; gentler, but slower absorption |
| Heme iron polypeptide | ~100% | ~12 mg per 12 mg capsule | Derived from animal sources; better absorption, fewer GI issues |
| Carbonyl iron | ~100% | ~45 mg per 45 mg dose | Slow-release; less toxic in overdose, gentler on stomach |
| Iron bisglycinate (chelated) | ~20% | ~25–30 mg per capsule | Highly absorbable, well tolerated, fewer side effects |
How Different Iron Forms Affect Hepcidin
| Iron Type | Effect on Hepcidin | Notes |
|---|---|---|
| Ferrous sulfate / fumarate / gluconate | Strongly increases hepcidin (especially at high doses) | Rapid, unbuffered iron spikes can cause hepcidin to rise within hours, reducing absorption of later doses. Daily high doses can become counterproductive. |
| Iron bisglycinate (chelated) | Mild to moderate increase | Gentler absorption and fewer spikes in serum iron; less hepcidin stimulation compared to ferrous salts. |
| Carbonyl iron | Mild increase | Slow release leads to more gradual absorption; may result in less hepcidin upregulation. |
| Heme iron polypeptide | Minimal effect on hepcidin | Absorbed via a separate mechanism (heme transporter); bypasses the usual regulatory pathway, making it useful in conditions with high hepcidin. |
| Iron protein succinylate (IPS) | Moderate and delayed increase | Slow, intestinal release reduces hepcidin response; may allow for better sustained absorption. |
| IV iron (e.g., ferric carboxymaltose) | Significant increase | Bypasses gut; can trigger high hepcidin due to large systemic iron load. |
