Ferrous fumarate

How it works

It provides elemental iron in the absorbable ferrous form, which is taken up in the duodenum and incorporated into haemoglobin to support erythropoiesis.

Prescribing in practice

• Iron salts are a leading cause of accidental poisoning fatalities in young children, so keep all preparations well out of reach and counsel on safe storage.
• Absorption is reduced by tea, antacids, calcium, and by chelation with tetracyclines, quinolones, levothyroxine and bisphosphonates, which should be separated in time.
• Gastrointestinal upset, constipation and dark stools are common and may improve by taking the dose with or after food at the cost of slightly reduced absorption.

Monitoring

Check haemoglobin and iron indices after a few weeks to confirm an adequate response, continuing treatment for a period after normalisation to replenish stores.

Counselling the patient

• Stools may turn black; this is harmless and expected.
• Keep iron tablets away from children as overdose can be dangerous.
• Avoid taking with tea, milk or indigestion remedies at the same time of day.

Evidence & guidelines

NICE guidance supports oral ferrous salts as first-line treatment for iron-deficiency anaemia, with parenteral iron reserved for intolerance or malabsorption.