Iron
Supplements · Minerals · Supplement, Typed Supps
Only take it if a blood test shows you are actually low.
Stage by stage
- Intake (Tablet or capsule): Absorbs far less efficiently than most minerals — typically only 10–30% of a dose.
- Digestion & absorption (DMT1 transporter): Stomach acid converts iron into an absorbable form, then a dedicated transporter (DMT1) pulls it in at the very start of the small intestine.
- Bloodstream (Carried by transferrin): Binds to transferrin, which ferries it through the blood.
- Bone marrow (Built into haemoglobin): Ends up built into haemoglobin, the molecule that carries oxygen in red blood cells.
What the evidence supports
- Correcting iron-deficiency anaemia — strong evidence. Unambiguous. Oral iron reliably restores haemoglobin and stores in people who are genuinely deficient.
- Reducing fatigue in people who are iron-deficient without anaemia — moderate evidence. Several trials show improvement where ferritin is low even with normal haemoglobin — most consistently in menstruating women.
- Improving energy in people with normal iron levels — insufficient evidence. No benefit, and a real downside: your body has no active way to get rid of excess iron.
- Improving endurance performance in non-deficient athletes — insufficient evidence. Correcting a deficiency helps. Adding more on top of normal stores does not.
Typical dose
15–65 mg elemental iron daily when treating a documented deficiency
Upper limit: 45 mg daily for adults
Timing
Absorbs best empty-stomach, but often taken with a little food for tolerance.
Time to effect
- 2–4 wks: Energy often starts improving.
- 3–6 mo: Iron stores fully rebuild.
Medication interactions
- Levothyroxine: Iron binds it in the gut and can meaningfully reduce absorption. Separate by at least four hours. (high)
- Tetracycline and quinolone antibiotics: Bind to iron and lose effectiveness. Separate doses by several hours. (high)
- Proton pump inhibitors and antacids: Less stomach acid means less iron converted to the absorbable form. (moderate)
- Levodopa: Iron reduces its absorption, which matters for Parkinson’s control. (high)
Common myth
“More iron is always better for energy.” In reality: Your body has no efficient way to excrete excess iron — supplementing without a confirmed deficiency can do more harm than good.
Food sources
Relevant movements
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