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Mineral

Iron (as Fermented Iron Bisglycinate)

Also known as: iron bisglycinate, fermented iron, chelated iron

A
Evidence

Iron is an essential mineral critical for oxygen transport and fetal development during pregnancy. The bisglycinate chelate form offers enhanced absorption and bioavailability with reduced GI irritation compared to ferrous salts.

Last reviewed June 2026 · Evidence graded from peer-reviewed research, not editorial opinion. Educational only — not medical advice.

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Primary uses

  • Oxygen transport
  • Prevention of gestational anemia
  • Fetal development and birth weight support
  • Energy metabolism

How it works

  • Component of hemoglobin and myoglobin
  • Cofactor for iron-dependent enzymes
  • Chelation improves intestinal absorption
  • Reduced ionic irritation to GI tract

Dosage

Typical range
27 mg daily (RDA for pregnant women)
Timing
morning on empty stomach preferred for absorption, but can take with food if GI upset occurs
With food
separate from calcium, zinc, and polyphenols by 2 hours when possible; vitamin C enhances absorption
Duration
throughout pregnancy and postpartum; continue if breastfeeding
Special populations
Pregnant women 27 mg/day; lactating women 9–10 mg/day; dosage may increase if anemia confirmed

Forms

  • iron bisglycinate· 70/100
  • ferrous fumarate· 70/100
  • ferrous sulfate· 70/100

Safety

Common side effects

  • constipation
  • nausea
  • dark stools

Contraindications

  • Hemochromatosis
  • sickle cell disease without supplementation indication

Products containing Iron (as Fermented Iron Bisglycinate)

Top-scoring supplements in our catalog that list Iron (as Fermented Iron Bisglycinate) on the label. Each product is graded on Formulate's ingredient-level rubric — dose accuracy, form, transparency, and third-party testing.

Thorne
Iron Bisglycinate
96
Transparent Labs
Grass-Fed Whey Protein Isolate
95
Complement
ForHer Hormone Balance and Longevity Multivitamin for Women
89
Thorne
Basic Prenatal
88
See all products →

Evidence notes

Extensive RCT evidence for iron supplementation in pregnancy; strong evidence that adequate iron prevents anemia and poor birth outcomes; chelated forms reduce side effects while maintaining efficacy.

Grade A: Multiple well-designed human trials support the main claims.

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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.