Benefits
Established Standard for Iron Deficiency
Ferrous sulfate is WHO-recommended first-line oral iron for iron deficiency anemia. Decades of clinical use across all populations — pregnant women, children, elderly, post-surgical, post-bleeding. Effective for raising hemoglobin and ferritin.
High Elemental Iron Content
~20% elemental iron by weight — among the higher-content forms. 325 mg ferrous sulfate provides 65 mg elemental iron. Cost-effective for delivering required iron amounts.
Lowest Cost Iron Supplement
Ferrous sulfate is the cheapest oral iron form — generic, OTC, and widely available. WHO and developing-world iron supplementation programs rely on ferrous sulfate for affordability and global access.
Effective in Iron Repletion
Despite GI side effects, ferrous sulfate reliably raises hemoglobin in IDA — meta-analyses show effective response over 8-12 weeks. Slow-release/enteric-coated formulations may improve tolerability while preserving absorption.
Pediatric Iron Deficiency
Liquid ferrous sulfate (drops, syrup) is widely used for pediatric iron deficiency — though staining of teeth is a concern with prolonged use; offered with straw and rinsing recommendations.
Mechanism of action
Ferrous (Fe²⁺) Form
Iron exists in two oxidation states: ferrous (Fe²⁺) and ferric (Fe³⁺). The body absorbs ferrous iron preferentially via DMT1 transporter in duodenal enterocytes. Ferric iron must be reduced before absorption — ferrous forms (sulfate, fumarate, gluconate) bypass this step.
DMT1 Transport
Divalent metal transporter 1 (DMT1) on duodenal enterocyte apical membrane absorbs Fe²⁺. Once inside, iron is exported via ferroportin to plasma transferrin for delivery to bone marrow (erythropoiesis), liver storage (ferritin), and other tissues.
Hepcidin Regulation
Hepcidin (liver-derived hormone) regulates iron absorption — high iron status raises hepcidin, blocking ferroportin and reducing absorption. Inflammation also raises hepcidin (functional iron deficiency in chronic disease).
Stomach Acid Dependence
Ferrous sulfate absorption is enhanced by gastric acid (low pH). PPIs and atrophic gastritis reduce iron absorption. Vitamin C improves absorption by reducing Fe³⁺ to Fe²⁺ and forming soluble complexes.
Clinical trials
Clinical reviews comparing ferrous sulfate vs ferric polymaltose for iron deficiency anemia treatment.
Pooled across IDA RCTs.
Ferrous sulfate produces 3-4× greater hemoglobin response than ferric polymaltose preparations. Established as standard treatment. Slow-release ferrous sulfate maintains efficacy with somewhat improved tolerability.
Systematic review examining tolerability of various oral iron supplements vs placebo. (Tolkien et al. 2015, PLoS ONE)
Pooled across iron supplement RCTs.
Ferrous sulfate had significantly higher rates of GI adverse events vs placebo: constipation, nausea, abdominal pain, metallic taste. Adherence is the major clinical limitation — 40-50% of patients reduce dose or discontinue due to side effects. Alternative forms (bisglycinate, fumarate, slow-release) may improve tolerability.
About this ingredient
Ferrous sulfate (FeSO4) is the WHO-recommended standard oral iron supplement — among the cheapest, most established, and most studied iron forms. CHEMICAL FORM: ferrous (Fe²⁺) iron — directly absorbable via DMT1 transporter; ferric (Fe³⁺) forms must first be reduced. Elemental iron content: ~20% by weight. Typical formulations: 325 mg ferrous sulfate tablet = ~65 mg elemental iron.
EVIDENCE-BASED USES: (1) IRON DEFICIENCY ANEMIA — first-line WHO-recommended; (2) Pregnancy iron supplementation (often combined with folate); (3) Pediatric iron deficiency (liquid forms; staining caution); (4) Post-bleeding iron repletion; (5) Vegetarian/vegan iron support.
CRITICAL CAUTIONS: (1) PEDIATRIC IRON POISONING — leading cause of pediatric fatal poisoning; child-resistant packaging mandatory; AVOID accidental ingestion; (2) HEMOCHROMATOSIS / iron overload disorders — AVOID; iron supplementation contraindicated; (3) GI INTOLERANCE — major adherence issue; 40-50% of patients reduce dose or quit; alternative forms (bisglycinate, fumarate, slow-release) may improve tolerability; (4) DRUG INTERACTIONS — chelates many drugs (tetracyclines, quinolones, bisphosphonates, levothyroxine, levodopa, mycophenolate); separate by 2-4 hours; (5) OXIDATIVE STRESS concern — ferrous sulfate generates reactive oxygen species in GI tract; some research suggests this contributes to mucosal inflammation; (6) PPI/H2 BLOCKER USERS — gastric acid suppression reduces iron absorption; take iron timing-spaced from acid suppressants; (7) PREGNANCY — iron supplementation is standard antenatal care; ferrous sulfate appropriate; (8) HEMOGLOBINOPATHIES (thalassemia minor) — iron supplementation may be inappropriate; consult hematology; (9) FUNCTIONAL IRON DEFICIENCY in chronic disease (high hepcidin) — oral iron poorly absorbed; IV iron may be needed; consult.