Only if deficiency is confirmed. Taken on alternate days and with vitamin C, it is absorbed better and is better tolerated.
Reduces fatigue, especially if there is iron deficiency/low ferritin
View the study (meta-analysis) →Review: heme iron (from meat) is absorbed better than non-heme (plant) iron, and non-heme absorption varies widely depending on other foods that enhance it (e.g., vitamin C) or inhibit it. The body does not eliminate excess iron: it regulates how much enters.
View the study (study) →⏱ 3 min read
Iron is one of the most essential minerals in the body: it is part of hemoglobin (which carries oxygen from the lungs to every cell in the body), of myoglobin (which stores it in muscle), and of countless enzymes involved in energy metabolism, neurotransmitter synthesis, and immunity; its deficiency is the most prevalent nutritional deficiency in the world, especially affecting women of childbearing age, young children, strict vegetarians, endurance athletes, and people with chronic blood loss.
Unlike most minerals and vitamins, iron requires more careful handling because the body has no efficient mechanism for eliminating the excess, which means that supplementation without a documented deficiency can accumulate and cause long-term oxidative tissue damage; the basic rules of clinical iron use are: measure before supplementing, dose only what is needed, and monitor the response.
The most important biomarker for assessing the body's iron status is serum ferritin: it reflects total iron stores and is the most sensitive indicator of deficiency (it falls before hemoglobin, which drops only once stores are already depleted); values below 30 ng/mL in healthy adults indicate functional deficiency and below 15 ng/mL indicate frank deficiency, although some clinical contexts (female athletes, cognitive decline, unexplained fatigue) suggest higher targets (50-100 ng/mL).
Hemoglobin, the classic marker of anemia, is less sensitive: many people have functional iron deficiency with symptomatic consequences (fatigue, reduced mental performance, hair loss) before hemoglobin falls below the normal range; measuring only hemoglobin and not ferritin is one of the most frequent diagnostic errors in primary care regarding iron management.
In documented iron-deficiency anemia (low hemoglobin + low ferritin), supplementation with 30-100 mg of elemental iron daily (typically ferrous sulfate, ferrous gluconate, or ferrous bisglycinate) for 3-6 months normalizes hemoglobin and, most importantly, replenishes ferritin stores; treatment should continue for several months after hemoglobin normalizes to ensure stable stores and prevent relapse.
In functional deficiency without anemia (low ferritin with normal hemoglobin), lower doses (20-50 mg/day) for 8-12 weeks usually resolve the associated symptoms (fatigue, exercise intolerance, mental sluggishness); in female athletes and in women of childbearing age with heavy periods, maintenance supplementation may be reasonable to avoid cyclical fluctuations in stores.
The classic ferrous salts (sulfate, fumarate, gluconate) are the most studied and the cheapest, but also the ones that cause the most gastrointestinal discomfort (constipation, nausea, epigastric pain, darkening of stools); ferrous bisglycinate and heme iron (from meat) are better tolerated and have better bioavailability in terms of percentage absorbed, which justifies their preferred use in people who do not tolerate the classic salts.
Newer intermittent iron regimens (one dose every 2-3 days instead of daily) have shown in recent studies that total absorption can be similar or even higher with fewer adverse effects, because continuous daily dosing raises hepcidin (a hormone that blocks intestinal absorption) and paradoxically reduces efficiency with each successive dose.
Iron accumulated in excess is toxic: it causes oxidative stress and liver, heart, and joint damage, and it is associated with a higher risk of several cancers in long epidemiological studies; people with hereditary hemochromatosis (frequency of 1 in 200 in Europeans), those who have received repeated transfusions, and adult men without chronic blood loss should not supplement iron without a documented deficiency.
Therapeutic doses are ideally taken on an empty stomach with vitamin C (which improves absorption) and separated by at least 2 hours from coffee, tea, dairy, calcium, and antacids (which inhibit it); if gastrointestinal discomfort is intolerable, taking iron with a light meal improves tolerance although it somewhat reduces absorption; in female athletes with heavy periods, a dose after each monthly period for 2-4 weeks may be more efficient than small continuous doses.
Information, not medical advice. Scientific evidence reflects the quality of the studies.