howtosupplement
Deficiency/Women/Cognition

Iron

Essential mineral that restores iron stores, improves fatigue from deficiency, and helps adults with low ferritin or high iron needs.

Iron

Iron

85
score
A
evidence
Caution
risk

Proven Benefits

01Corrects iron-deficiency anemia
02Prevents maternal anemia
03Reduces fatigue when iron is low
04Improves attention and memory
05Improves restless legs symptoms
06May reduce hair shedding
07May support immune function

Chemical Forms

Recommended
  • Ferrous bisglycinate
  • Ferrous sulfate
  • Ferrous fumarate
  • Ferrous gluconate
Avoid
  • Ferric iron salts (lower absorption)
  • Enteric-coated or delayed-release iron (can reduce absorption in the duodenum)
Expert Note

Ferrous forms are generally absorbed better than ferric forms. Ferrous bisglycinate is often easier on the stomach while remaining effective; ferrous sulfate and fumarate are the most studied, low-cost options. Enteric-coated tablets can underperform because most iron absorption happens in the duodenum.

Protocol

Amount
25-65 mg elemental iron
Frequency
Once daily or every other day
When
Best on an empty stomach with water or vitamin C; if it causes nausea, take with a small meal and keep it away from calcium, coffee, tea, and antacids.

Condition-Based Dosing

Ferritin < 30 ng/mL without anemia
25-40 mg elemental iron once daily or every other day for 8-12 weeks.
Iron deficiency anemia (low hemoglobin + low ferritin)
40-65 mg elemental iron once daily or every other day for at least 8-12 weeks, then continue about 2-3 months after normalization.
Pregnancy, no confirmed deficiency
27 mg elemental iron daily, usually through a prenatal.
Frequent blood donor, vegetarian, or vegan with borderline ferritin
18-27 mg daily or 25-40 mg every other day.

Safety & Limits

Upper Safe Limit
45 mg/day elemental iron (IOM UL for adults; higher short-term doses are used only for confirmed deficiency under medical supervision)
Cycling
Safe for continuous use

Contraindications

Hemochromatosis or other iron-overload disorders — supplementation can rapidly worsen overload
Thalassemia, sideroblastic anemia, or repeated transfusions — higher overload risk unless deficiency is confirmed
Non-deficient adults — routine supplementation can cause unnecessary iron accumulation over time
Unexplained anemia or GI bleeding — self-treatment may delay diagnosis of a serious cause
Active peptic ulcer, severe gastritis, or inflammatory bowel disease flare — oral iron may worsen GI irritation
Chronic liver disease — excess iron can accumulate more easily
Children — accidental overdose is a medical emergency; keep locked away

Synergies

Vitamin C

Vitamin C reduces ferric iron to the more absorbable ferrous form and can partly offset absorption blockers from plant-based meals.

Folate

Folate supports DNA synthesis and red blood cell production, so co-deficiency can blunt recovery from anemia.

Vitamin B12

B12 deficiency can coexist with iron deficiency and prevent full normalization of CBC markers if left uncorrected.

Avoid Combining With

  • ✕Calcium supplements or dairy at the same time (wait 2+ hours — competes for absorption)
  • ✕Coffee or tea within 1 hour (polyphenols and tannins reduce absorption)
  • ✕High-phytate bran or large whole-grain meals (can bind non-heme iron)
  • ✕Antacids, PPIs, and H2 blockers (lower stomach acid reduces absorption)
  • ✕Levothyroxine (separate by at least 4 hours — mutual absorption interference)
  • ✕Tetracycline or fluoroquinolone antibiotics (separate by 2-6 hours — chelation reduces absorption)
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