Pharmacology · Antianaemia agents (iron, folic acid, vitamin B12)
Ferrous sulfate !
The standard oral iron salt for treating and preventing iron-deficiency anaemia. Gut upset is common; overdose is dangerous for children.
Updated 2026-11-01
The figure shows human serum transferrin carrying two ferric iron ions; replacement iron travels in the blood this way to the marrow.
Mechanism of action
Ferrous (Fe²⁺) iron is absorbed in the duodenum by the divalent metal transporter, leaves the gut cell through ferroportin and is carried by transferrin to the marrow, where it is built into haem. The liver hormone hepcidin blocks ferroportin, so inflammation reduces absorption, and a high iron dose raises hepcidin for a day or so, which is why intermittent dosing can be absorbed as well as daily dosing.
- Iron is absorbed or released into the blood
- Transferrin carries it to the bone marrow
- Red cell precursors build it into haem
- Haemoglobin rises and stores (ferritin) refill
Pharmacokinetics
- Absorption
- Duodenum and upper jejunum; reduced by food and antacids; enteric-coated and slow-release forms are absorbed poorly
- Distribution
- Carried by transferrin; stored as ferritin
- Elimination
- No regulated excretion route: small losses come from shed cells, bile and blood
- Onset and duration
- Reticulocytes rise within days; haemoglobin recovers over weeks
Indications
- Treatment of iron-deficiency anaemia (after looking for the source of iron loss) Iron deficiency anaemia →
- Prevention of iron deficiency in pregnancy and in at-risk children
Adverse effects
Common
- Constipation or diarrhoea
- Nausea and stomach pain
- Tooth staining with liquid forms
Contraindications
- Anaemias not caused by iron deficiency, such as haemolytic anaemia
- Caution with peptic ulcer or gastrointestinal bleeding
Key interactions
- Tetracyclines (doxycycline, minocycline, tetracycline)
- Iron binds them in the gut; the doses are separated by hours
- Antacids and food
- Reduce iron absorption
What is monitored
- Haemoglobin and reticulocytes
- Ferritin to confirm that stores refill
- Adherence and gut tolerance
Administration and safety
- Oral; best absorbed on an empty stomach, but it may be taken with food if gut upset limits adherence
- Liquid forms can stain teeth
- Stored out of reach of children, in child-resistant containers
Nursing care
- Explain that constipation and stomach upset are common and usually manageable
- Teach how to separate it from tetracyclines and antacids
- Warn families about the danger of accidental ingestion by children
- Check that the cause of iron loss (menstrual, gastrointestinal, parasites) is being investigated
Pregnancy and breastfeeding
Iron needs rise in pregnancy; iron, often with folic acid, is routinely used to prevent and treat deficiency.
Test yourself
Think of the answer, then tap the question to see it.
Which hormone limits iron absorption by blocking ferroportin?
Hepcidin.
What two things reduce oral iron absorption?
Food and antacids (also enteric-coated forms).
What is the antidote for severe iron poisoning?
Deferoxamine.
Which antibiotics should be separated from iron?
Tetracyclines such as doxycycline.
Related drugs
Related conditions
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Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: DailyMed - FERROUS SULFATE tablet (DailyMed (U.S. National Library of Medicine), 2026); Iron Supplements: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2025); Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed., ch. 45 (McGraw Hill, 2023); Farmacología básica y clínica (Katzung), 16.ª ed., cap. 33 (McGraw Hill, 2025).
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Representative model, for educational purposes only.