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.
Last reviewed June 2026 · Evidence graded from peer-reviewed research, not editorial opinion. Educational only — not medical advice.
Every Iron product we have scored
| # | Product | Score | Per serving |
|---|---|---|---|
| 1 | Thorne Iron Bisglycinate | 96 A | $0.27 |
| 2 | Transparent Labs Grass-Fed Whey Protein Isolate | 95 A | $2.00 |
| 3 | Complement ForHer Hormone Balance and Longevity Multivitamin for Women | 89 A | $0.67 |
| 4 | Thorne Basic Prenatal | 88 A | $1.23 |
| 5 | Ritual Essential Prenatal | 88 A | $0.65 |
| 6 | Pure Encapsulations Iron-C | 87 A | $0.32 |
| 7 | Solgar Gentle Iron | 87 A | $0.09 |
| 8 | Transparent Labs Multivitamin | 86 A- | $1.33 |
| 9 | Complement Restore | 86 A- | $1.90 |
| 10 | Seed AM-02™ Energy + Focus Supplement | 86 A- | $1.17 |
| 11 | Garden of Life Primal Defense Ultra | 86 A- | $0.56 |
| 12 | Garden of Life Organics Prenatal Multi | 86 A- | $1.14 |
Scored on dose accuracy, form, label transparency and third-party testing. Per-serving cost is list price divided by servings per container. No brand pays to be listed or ranked.
Common questions
How much Iron should I take?
The typical range is 18-45mg daily when deficient. Until levels normalize
When should I take Iron?
Empty stomach or with vitamin C. Optional, may reduce absorption.
Which form of Iron is best?
Bisglycinate — Gentle, well-absorbed. Other forms in the catalog: Ferrous sulfate, Heme iron, Iron bisglycinate, Heme iron polypeptide.
Is Iron safe?
Commonly reported: Constipation, Nausea, Dark stools. Serious warnings: Toxicity at high doses, Hemochromatosis. Test levels first
Which Iron supplement scores highest?
Thorne Iron Bisglycinate, at 96/100. Scored on dose accuracy, form, label transparency and third-party testing — no brand pays to be listed or ranked.
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
What systematic reviews concluded
Outcomes that systematic reviews of Iron reached a verdict on: 2 with a benefit, 2 unclear. Each is quoted from a review and linked to it on PubMed. How these were read.
Reviews found a benefit (2)
“At 6 months, liposomal iron produced a significantly greater increase in hemoglobin compared with conventional iron (MD 0.96 g/dL, 95% CI 0.09-1.82; P = 0.03), although heterogeneity was substantial (I2 = 92.9%).” PMID 42183880 · 3 reviews
“Liposomal iron was associated with fewer adverse events (RR 0.29; P = 0.02) and lower risk of constipation (RR 0.56; P = 0.02).” PMID 42183880 · 3 reviews
Not enough to say: iron stores/deficiency in blood donors; androgenetic alopecia.
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
- 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
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Medical disclaimer. This page is educational and does not replace advice from a qualified healthcare provider. Individual needs and risks vary — consult a professional before starting, stopping, or combining supplements, especially if you are pregnant or nursing, taking medication, or managing a health condition.