High Iron and Ferritin Do Not Block Magnesium Absorption Into Tissues
Based on available clinical evidence, there is no established mechanism by which elevated iron or ferritin levels prevent magnesium absorption into tissues in humans. The relationship between these minerals is more complex than simple competitive inhibition.
The Actual Relationship Between Iron and Magnesium
Magnesium Deficiency Affects Iron Metabolism—Not the Reverse
- Magnesium deficiency actually increases iron absorption and accumulation in tissues, not the other way around 1, 2.
- In magnesium-deficient states, iron absorption from the intestine is significantly elevated, leading to increased plasma iron levels and tissue iron deposition, particularly in the liver and spleen 2.
- Magnesium-deficient rats with dietary iron overload show enormously elevated saturation of iron binding capacity and abnormal iron metabolism, losing homeostatic regulation of plasma iron 1.
No Evidence That High Iron Blocks Magnesium
- The clinical guidelines on iron metabolism and ferritin management make no mention of iron interfering with magnesium absorption or tissue uptake 3, 4, 5.
- Low magnesium concentrations can exacerbate iron deficiency, but the reverse mechanism (high iron blocking magnesium) is not documented 6.
What High Ferritin Actually Indicates
Ferritin as an Inflammatory Marker
- Elevated ferritin is primarily an acute phase reactant that increases during inflammation, not necessarily indicating true iron overload 3, 5.
- Ferritin can be elevated in the absence of increased iron stores in patients with inflammatory conditions, chronic liver disease, and malignancies 3.
When High Ferritin Reflects True Iron Overload
- In hereditary hemochromatosis (HFE), tissue iron overload occurs when ferritin exceeds 200-300 μg/L in combination with elevated transferrin saturation 3.
- Organ damage from iron overload typically requires dramatically higher ferritin levels (>7,500 ng/mL) and occurs primarily in transfusional hemosiderosis 5.
Clinical Implications
If You Have High Iron/Ferritin and Suspect Magnesium Issues
- Evaluate magnesium status independently—serum magnesium levels, clinical symptoms of deficiency (muscle cramps, arrhythmias, neuromuscular irritability), and consider RBC magnesium if indicated 6.
- Address the underlying cause of elevated ferritin: inflammation, liver disease, malignancy, or true iron overload 3, 4.
- Magnesium supplementation should be based on documented deficiency, not on assumptions about iron interference 6.
Important Caveats
- Magnesium hydroxide can reduce iron absorption when given shortly after iron ingestion (within 30-60 minutes), but this is a pharmacological interaction during supplementation, not a physiological tissue absorption issue 7, 8.
- This interaction is relevant only when taking oral iron and magnesium supplements simultaneously—it does not mean that having high body iron stores blocks magnesium tissue uptake 7, 8.