Iron
TL;DR
Essential mineral for oxygen transport in the blood (hemoglobin)
Moderate evidence for cognitive function in those with deficiency
Low evidence for hearing loss
Dangerous in excess; can cause oxidative damage (hemochromatosis)
Very cheap: ~$5-10/month
Best for: Anemia, restless leg syndrome, cognitive fog in deficient women
What it is
Iron is the 'oxygen carrier' of the body. It is the central part of hemoglobin, the protein in red blood cells that carries oxygen from your lungs to your tissues. It's also involved in energy production and DNA synthesis.
Iron is one of the few supplements you should never take unless you have confirmed a deficiency through a blood test. Men and post-menopausal women rarely need iron, while menstruating women and vegetarians are at the highest risk for deficiency.
What the research says
Iron is a 'Goldilocks' nutrient for the brain. Deficiency. 'Anemic fog' is real. A study in the American Journal of Clinical Nutrition found that iron-deficient women had significant improvements in memory and attention after iron supplementation. Excess. Conversely, too much iron in the brain is associated with Alzheimer's and oxidative stress. Verdict. Supplement only if your Ferritin (stored iron) is low.
There is a statistical link between anemia and hearing loss. Evidence. Large observational studies have found that people with Iron Deficiency Anemia (IDA) are twice as likely to have hearing loss. The theory is that the inner ear is highly sensitive to oxygen supply, and anemia starves it of oxygen. However, trials showing that iron supplements treat existing hearing loss are lacking.
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Safety
Iron is the leading cause of accidental poisoning deaths in children. It causes significant GI upset (constipation, black stools, nausea). Excess iron is a pro-oxidant that can damage the liver and heart.
Interactions
- Everything: Iron binds to almost everything. Separate from Calcium, Thyroid Meds, and Antibiotics by at least 2-4 hours.
- Vitamin C: Enhances iron absorption significantly.
Dosing
Standard Dose: 18-65 mg of elemental iron, depending on deficiency level. Form: Iron Bisglycinate is much easier on the stomach and causes less constipation than Ferrous Sulfate.
Cost
Cheap. $5-10 per month.
The bottom line
Iron is a 'prescription' supplement. Do not take it unless a blood test proves you need it. If you are anemic, it will change your life; if you aren't, it may harm you.
Sources for this page include published meta-analyses, systematic reviews, and NIH dietary supplement fact sheets. All claims reflect the evidence as of early 2026.
This is not medical advice. Consult your healthcare provider before starting any supplement, especially if you take medications.