Mineral
Iron
Also known as: Fe, Iron ion, Ferrous, Ferric
Essential for oxygen transport and immune cell function, but excess can feed pathogens. Important to test before supplementing.
Daily target & upper limit
18 mg / day · UL 45 mgIron has an established daily reference intake. See best forms, label synonyms, upper-limit warnings, and top-scoring supplements:
Iron dosage reference →Primary uses
- Hair loss
- Hair growth
- Ferritin support
- Energy
- Oxygen transport
- Fatigue
- Anemia prevention
- Immune cell function
- Anemia treatment
- Immune function
- Cognitive function
How it works
- Hemoglobin component
- Myoglobin in muscles
- Electron transport chain
- Enzyme cofactor
Dosage
- Typical range
- 18-45mg daily when deficient
- Timing
- Empty stomach or with vitamin C
- With food
- Optional, may reduce absorption
- Duration
- Until levels normalize
- Special populations
- Women, vegetarians
Forms
- Bisglycinate
- Ferrous sulfate
- Heme iron
- Iron bisglycinate
- Heme iron polypeptide
Safety
Common side effects
- Constipation
- Nausea
- Dark stools
Contraindications
- Hemochromatosis
- Iron overload
Products containing Iron
Top-scoring supplements in our catalog that list Iron on the label. Each product is graded on Formulate's ingredient-level rubric — dose accuracy, form, transparency, and third-party testing.
Known interactions
- Cautionwith zinc
Zinc and iron compete for absorption
- Warningwith calcium
Calcium significantly reduces iron absorption
- Synergywith vitamin c
Vitamin C dramatically enhances iron absorption
- Cautionwith antacids
Antacids significantly reduce iron absorption
- Warningwith thyroid medication
Iron reduces levothyroxine absorption
- Synergywith vitamin a
Vitamin A enhances iron absorption
Evidence notes
Essential mineral critical for oxygen transport
Grade A: Multiple well-designed human trials support the main claims.
Cited research for Iron
Clinical studies referenced across Formulate guides that mention iron. Each links to the full study page with PubMed source + the guides that cite it.
- Stoffel NU, Cercamondi CI, Brittenham G, et al. (2017)Blood
Oral iron supplements increase hepcidin and decrease iron absorption from daily or twice-daily doses in iron-depleted young women
- Hurrell R, Egli I (2010)American Journal of Clinical Nutrition
Iron bioavailability and dietary reference values
- Hallberg and Hulthén (2000)American Journal of Clinical Nutrition
Prediction of dietary iron absorption: an algorithm for calculating absorption and bioavailability
Related in Mineral
Check a full stack
Formulate's free interaction checker lets you paste in any combination of supplements and medications at once — every pairing flags severity, timing, and cited evidence.
Open the checkerMedical disclaimer. This page is educational and does not replace advice from a qualified healthcare provider.