Iron is essential for haemoglobin — the protein in red blood cells that carries oxygen. When stores are depleted, haemoglobin production falls and oxygen delivery to tissues drops.
Haem iron (from meat, poultry, seafood) is absorbed at 15–35%. Non-haem iron (from legumes, fortified cereals, dark leafy vegetables, seeds) is absorbed at 2–20%, but absorption rises substantially when vitamin C is consumed at the same meal. Conversely, tea, coffee, calcium, and phytates (in wholegrains and legumes) reduce non-haem iron absorption.
Women of reproductive age, pregnant women, children, and people eating predominantly plant-based diets have higher requirements and greater risk. Diagnosis requires blood tests (serum ferritin, full blood count); treatment typically involves dietary optimisation and, where confirmed deficient, iron supplementation under medical supervision. Self-prescribing iron supplements is not advisable — excess iron has its own risks.