Iron oral (salts: sulfate, bisglycinate, fumarate, gluconate, polymaltose; heme iron polypeptide, lactoferrin)

Oral iron preparations; antianaemic agents

ATC code: B03AA (Iron bivalent, oral preparations)

Brand names

Slow-FE, Ferro-Sequels, Feosol, Proferrin (heme iron polypeptide)

Mechanism of action

Iron is incorporated into haem of haemoglobin and myoglobin and into iron-sulphur clusters of the respiratory chain. Ferrous salts (sulfate, bisglycinate, fumarate, gluconate) are absorbed in the duodenum via DMT1 and regulated by hepcidin. Ferric polymaltose releases iron more slowly, causes fewer GI side effects but works more slowly in severe anaemia. Heme iron in hemoglobin polypeptide and bovine lactoferrin use a separate uptake pathway (HCP1) and are less studied in RCTs. Hepcidin suppresses absorption after each dose – this is why current and guidelines favour alternate-day dosing over daily.

Indications

Iron deficiency anemia

First line

Oral iron is first-line for iron-deficiency anaemia. AEMPS and approve all main salts. NG8 2024 and British Society for Haematology 2021 recommend 40-100 mg of elemental iron on alternate days: alternate-day dosing yields the same haemoglobin rise as daily and is better tolerated. Haemoglobin and ferritin are checked at 4-8 weeks. If levels do not rise over 2-3 months a search for the cause (ongoing blood loss, malabsorption) and switch to IV iron are warranted. Of iHerb forms, sulfate is cheaper and most studied; bisglycinate claims better tolerability at comparable bioavailability.

In oral intolerance, severe anaemia (haemoglobin below 70 g/L), inflammatory bowel disease, or late pregnancy with anaemia, intravenous iron is used.

Sources

Iron supplementation in pregnancy

First line

Iron deficiency prevention in pregnancy. and recommend 30-60 mg of elemental iron daily or alternate-day from the second trimester, especially with low baseline ferritin. SEGO applies a similar regimen in Spain. AEMPS approves Tardyferon and Ferro Sanol for this indication. Self-prescribing high-dose iron without testing is rarely warranted: in patients with HFE mutations (asymptomatic haemochromatosis) iron overload accelerates hepatic damage.

Sources

Iron deficiency without anaemia

Individual decision

Iron use in low ferritin without anaemia (endurance athletes, after blood donation, with heavy menstrual bleeding) is decided individually. British Society for Haematology 2021 accepts treatment at ferritin below 30 mcg/L with fatigue symptoms. NIH ODS 2024 states that routine intake in asymptomatic people with normal haemoglobin is unjustified. The dose is set by tolerability – 40-60 mg of elemental iron on alternate days. Ferritin is rechecked at 8-12 weeks. Ferritin and transferrin testing precede a course, not «iron for energy» on Instagram advice.

Sources

Marketing claims without evidence base

The drug is promoted for these uses outside international guidelines. Each entry below is analyzed against AEMPS, FDA, EMA, Cochrane and major RCTs.

Chronic fatigue

Not recommended

This refers to chronic fatigue WITHOUT confirmed iron deficiency. Here iron gives no benefit, and taking it without an indication risks constipation, nausea, and iron overload. If iron deficiency is confirmed by tests (ferritin and so on), iron is indicated and effective, but those are separate indications: iron deficiency anemia and iron deficiency without anemia. Fatigue should first prompt checking iron stores, not taking iron blindly.

Sources

Practical notes

Timing and administration

Take on an empty stomach 30–60 minutes before meals, with water or a vitamin C-containing drink (enhances absorption). If dyspepsia is intolerable, take with food, but absorption drops 2–3 fold. Alternate-day dosing (100–200 mg) in non-pregnant women is more effective than daily dosing per the Stoffel 2017 RCTs.

Dose titration

Elemental iron dose: 60–100 mg daily when given daily; 100–200 mg on alternate days. One Sorbifer Durules tablet contains 100 mg elemental iron, Maltofer syrup 10 mg/mL, Tot'hema ampoule 50 mg. Prophylactic pregnancy dose is 30–60 mg daily, treatment dose 100–200 mg daily.

Monitoring

At 2 weeks, check reticulocytes (should rise). At 4 weeks, check haemoglobin (expected rise 10–20 g/L). If no rise, reconsider the diagnosis: exclude ongoing bleeding, absorption problems, or a dosing error. After haemoglobin normalises, check ferritin every 2–3 months for a year – therapy continues until ferritin exceeds 50 µg/L.

Food and drinks

Reduce absorption: calcium (dairy, calcium supplements), tea, coffee, whole grains with phytates, antacids, proton pump inhibitors. Separate iron and these items by at least 2 hours. Quinolones, tetracyclines, levothyroxine, and levodopa form insoluble complexes with iron – separate by at least 4 hours.

Common myths

Myth: “all women need iron for energy”. Fact: with normal ferritin, iron has no effect on fatigue. Unwarranted use increases oxidative stress. Check ferritin and complete blood count before buying an iron supplement.

Myth: “Maltofer is safer than Sorbifer because it's ferric”. Fact: safety differences with oral use are minor. Ferrous iron (Sorbifer, Feosol) is more effective at correcting deficiency; ferric forms (Maltofer) irritate the gastrointestinal tract less. The choice is a matter of tolerance.

Myth: “pomegranate juice and buckwheat raise haemoglobin”. Fact: non-haem iron from plant sources (buckwheat, pomegranate, apples) is absorbed less efficiently than haem iron from animal sources (red meat, liver, shellfish). In established anaemia, dietary correction is adjunctive – iron preparations are the main therapy.

Drug–nutrient interactions

Calcium

Calcium reduces iron absorption by 40–60% at concurrent doses above 300 mg. Iron and calcium are separated by 2 hours. In long-term therapy with both, timing is planned to different parts of the day.

Source: BSG: British Society of Gastroenterology guidelines for the management of iron deficiency anaemia in adults (2021)

Vitamin C (ascorbic acid)

Ascorbic acid 100–200 mg increases ferrous iron absorption by 10–15% by reducing Fe³⁺ to Fe²⁺. The effect is stronger with concurrent than separated dosing. In guidance, vitamin C is optional with iron therapy – not considered mandatory.

Source: BSG: British Society of Gastroenterology guidelines for the management of iron deficiency anaemia in adults (2021)

Drug–drug interactions

1 pair found. Sorted from critical to minor.

Minor

Doxycycline

Tetracyclines

Mechanism

Iron forms non-absorbable chelates with tetracyclines in the gut (as with the doxycycline-calcium pair). Doxycycline bioavailability falls by 50–80%.

Symptoms

Persistent infection symptoms 48–72 hours after antibiotic start, risk of clinical failure.

Management

Take doxycycline 2 hours before or 6 hours after iron supplements. Same interval applies to calcium, magnesium, zinc, and aluminium-containing antacids. If timing separation is impossible (e.g. severe iron deficiency), choose an alternative antibiotic (amoxicillin, a cephalosporin).

Sources

FDA: Vibramycin (doxycycline) prescribing information (2014)

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Official sources

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GRLS

Russian State Register of Medicines

Safety

Contraindications

Hypersensitivity to iron or excipients
Haemochromatosis and other iron overload syndromes
Haemolytic anaemias without confirmed iron deficiency
Recurrent blood transfusions (overload risk)
Active peptic ulcer and active intestinal bleeding

Serious adverse effects

Acute overdose (especially in children) with shock, metabolic acidosis and hepatic injury
Iron overload with long-term high-dose use without indication
Severe gastrointestinal bleeding in patients with active ulcers

Common adverse effects

Nausea, metallic taste
Constipation, less often diarrhoea
Epigastric pain
Dark stools (normal, not melaena)
Tooth staining with liquid formulations

Uncommon adverse effects

Tooth staining with liquid forms without a straw (reversible)
Skin rash, pruritus

PregnancyFDA A

FDA Category A at usual doses for prevention and treatment of iron deficiency. AEMPS and SEGO permit and encourage use in confirmed deficiency. High doses without indication in non-anaemic pregnant women are unjustified and raise gestational diabetes and pre-eclampsia risk per observational studies.

Breastfeeding

Compatible. Hale L1. Breast milk iron concentration is regulated and barely depends on maternal intake. eLactancia rates the risk as minimal.

Calculate RID

Reference information, not a clinical decision. Discuss feeding pauses or changes with your physician or an IBCLC.

Frequently asked

What is Iron oral (salts: sulfate, bisglycinate, fumarate, gluconate, polymaltose; heme iron polypeptide, lactoferrin) used for?

Iron oral (salts: sulfate, bisglycinate, fumarate, gluconate, polymaltose; heme iron polypeptide, lactoferrin) is evaluated for the following indications with varying evidence strength: Iron deficiency anemia (evidence tier A), Iron supplementation in pregnancy (evidence tier A), Iron deficiency without anaemia (evidence tier B). See the full indication matrix with dosing and citations above on this page.

What are the side effects of Iron oral (salts: sulfate, bisglycinate, fumarate, gluconate, polymaltose; heme iron polypeptide, lactoferrin)?

Common side effects of Iron oral (salts: sulfate, bisglycinate, fumarate, gluconate, polymaltose; heme iron polypeptide, lactoferrin) (≥ 1 in 100): Nausea, metallic taste, Constipation, less often diarrhoea, Epigastric pain, Dark stools (normal, not melaena), Tooth staining with liquid formulations. See the Safety section for uncommon and serious reactions.

Is Iron oral (salts: sulfate, bisglycinate, fumarate, gluconate, polymaltose; heme iron polypeptide, lactoferrin) safe during pregnancy?

FDA category A. FDA Category A at usual doses for prevention and treatment of iron deficiency. AEMPS and SEGO permit and encourage use in confirmed deficiency. High doses without indication in non-anaemic pregnant women are unjustified and raise gestational diabetes and pre-eclampsia risk per observational studies.

Is Iron oral (salts: sulfate, bisglycinate, fumarate, gluconate, polymaltose; heme iron polypeptide, lactoferrin) compatible with breastfeeding?

Compatible. Hale L1. Breast milk iron concentration is regulated and barely depends on maternal intake. eLactancia rates the risk as minimal.

Who should not take Iron oral (salts: sulfate, bisglycinate, fumarate, gluconate, polymaltose; heme iron polypeptide, lactoferrin)?

Iron oral (salts: sulfate, bisglycinate, fumarate, gluconate, polymaltose; heme iron polypeptide, lactoferrin) is contraindicated in: Hypersensitivity to iron or excipients; Haemochromatosis and other iron overload syndromes; Haemolytic anaemias without confirmed iron deficiency; Recurrent blood transfusions (overload risk); Active peptic ulcer and active intestinal bleeding. Full list in the Safety section.

“all women need iron for energy”

with normal ferritin, iron has no effect on fatigue. Unwarranted use increases oxidative stress. Check ferritin and complete blood count before buying an iron supplement.

“Maltofer is safer than Sorbifer because it's ferric”

safety differences with oral use are minor. Ferrous iron (Sorbifer, Feosol) is more effective at correcting deficiency; ferric forms (Maltofer) irritate the gastrointestinal tract less. The choice is a matter of tolerance.

“pomegranate juice and buckwheat raise haemoglobin”

non-haem iron from plant sources (buckwheat, pomegranate, apples) is absorbed less efficiently than haem iron from animal sources (red meat, liver, shellfish). In established anaemia, dietary correction is adjunctive – iron preparations are the main therapy.

Mechanism of action

Practical notes

Timing and administration

Dose titration

Monitoring

Food and drinks

Common myths

Drug–nutrient interactions

Calcium

Source: BSG: British Society of Gastroenterology guidelines for the management of iron deficiency anaemia in adults (2021)

Vitamin C (ascorbic acid)

Source: BSG: British Society of Gastroenterology guidelines for the management of iron deficiency anaemia in adults (2021)

Drug–drug interactions

1 pair found. Sorted from critical to minor.

Minor

Doxycycline

Tetracyclines

Mechanism

Iron forms non-absorbable chelates with tetracyclines in the gut (as with the doxycycline-calcium pair). Doxycycline bioavailability falls by 50–80%.

Symptoms

Persistent infection symptoms 48–72 hours after antibiotic start, risk of clinical failure.

Management

Sources

FDA: Vibramycin (doxycycline) prescribing information (2014)

Pair details →

Safety

Contraindications

Hypersensitivity to iron or excipients
Haemochromatosis and other iron overload syndromes
Haemolytic anaemias without confirmed iron deficiency
Recurrent blood transfusions (overload risk)
Active peptic ulcer and active intestinal bleeding

Serious adverse effects

Acute overdose (especially in children) with shock, metabolic acidosis and hepatic injury
Iron overload with long-term high-dose use without indication
Severe gastrointestinal bleeding in patients with active ulcers

Common adverse effects

Nausea, metallic taste
Constipation, less often diarrhoea
Epigastric pain
Dark stools (normal, not melaena)
Tooth staining with liquid formulations

Uncommon adverse effects

Tooth staining with liquid forms without a straw (reversible)
Skin rash, pruritus

PregnancyFDA A

Breastfeeding

Compatible. Hale L1. Breast milk iron concentration is regulated and barely depends on maternal intake. eLactancia rates the risk as minimal.

Calculate RID

Reference information, not a clinical decision. Discuss feeding pauses or changes with your physician or an IBCLC.

Frequently asked

What is Iron oral (salts: sulfate, bisglycinate, fumarate, gluconate, polymaltose; heme iron polypeptide, lactoferrin) used for?

What are the side effects of Iron oral (salts: sulfate, bisglycinate, fumarate, gluconate, polymaltose; heme iron polypeptide, lactoferrin)?

Is Iron oral (salts: sulfate, bisglycinate, fumarate, gluconate, polymaltose; heme iron polypeptide, lactoferrin) safe during pregnancy?

Is Iron oral (salts: sulfate, bisglycinate, fumarate, gluconate, polymaltose; heme iron polypeptide, lactoferrin) compatible with breastfeeding?

Compatible. Hale L1. Breast milk iron concentration is regulated and barely depends on maternal intake. eLactancia rates the risk as minimal.

Who should not take Iron oral (salts: sulfate, bisglycinate, fumarate, gluconate, polymaltose; heme iron polypeptide, lactoferrin)?

“all women need iron for energy”

with normal ferritin, iron has no effect on fatigue. Unwarranted use increases oxidative stress. Check ferritin and complete blood count before buying an iron supplement.

“Maltofer is safer than Sorbifer because it's ferric”

“pomegranate juice and buckwheat raise haemoglobin”