Iron
Commonly used for
EnergyAthletic Performance
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What is it? / Overview
Iron is necessary to produce hemoglobin which carries oxygen throughout the body. When iron stores are low fatigue, reduced exercise capacity, and anemia develop. Supplementation restores iron stores when deficiency is confirmed.
How is it used? / Administration
Form: Ferrous bisglycinate (better tolerated) or ferrous sulfate (standard first-line)
Typical dose studied: 25–65 mg elemental iron/day or every other day
Timing: Empty stomach if tolerated; with vitamin C; avoid calcium, coffee, tea within 1–2 hrs
Bisglycinate better tolerated than sulfate. Must confirm deficiency via labs — do not supplement iron without testing.
What does it pair with?
Pairs well with:
Vitamin C increases how well iron is absorbed — Vitamin C increases non-heme iron absorption.
Best taken separately from:
Calcium can interfere with iron absorption — commonly recommended to take iron and calcium supplements at different times.
Supplemental iron at 25 mg or more, taken at the same time, can reduce zinc absorption.
How well does it work? / Evidence
✓ Well-established
Who should avoid it?
Avoid with: Hemochromatosis / Iron overload
Interacts with: Separate from levothyroxine, tetracyclines, fluoroquinolones, bisphosphonates
Already taking it? Do not continue indefinitely without repeat ferritin and iron studies. Identify underlying cause. Active infection can transiently raise ferritin and lower iron absorption/utilization -- if acutely unwell, this is worth mentioning to a doctor rather than assuming supplementation is off-limits outright.
Research & references
Camaschella C. (2015). Iron-Deficiency Anemia. NEJM. Stoffel NU et al. (2017). Iron Absorption from Oral Supplements. Lancet Haematology. WHO Guideline: Daily Iron Supplementation.
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