Anaemia and Iron Deficiency

Anaemia means that the haemoglobin concentration in blood is below the appropriate reference level, reducing its capacity to carry oxygen. Iron deficiency means that the body's available iron is insufficient to meet its needs. They overlap but are not interchangeable: iron deficiency can exist before anaemia develops, and anaemia can arise without iron deficiency.

What each condition measures

Anaemia describes a blood abnormality, whereas iron deficiency describes an underlying nutrient deficit. Distinguishing them requires different measurements.

• Haemoglobin concentration identifies anaemia using cut-offs appropriate to factors such as age, sex and pregnancy status; it does not establish the cause.
• Serum ferritin helps assess iron stores. A low value supports iron deficiency, but infection or inflammation can raise ferritin and conceal depleted stores.
• Iron-deficiency anaemia is the overlap: iron shortage has progressed sufficiently to impair haemoglobin production and cause anaemia.
• Consequently, the prevalence of anaemia in a population cannot be treated as the prevalence of iron deficiency.

Why anaemia has multiple causes

Anaemia can result from reduced red-cell production, blood loss, or increased red-cell destruction. Iron deficiency is one important cause within this broader framework.

• Iron deficiency can arise from inadequate intake, poor absorption, increased requirements during growth or pregnancy, and blood loss.
• Deficiencies of folate or vitamin B12 can impair red-cell production even when iron supply is adequate.
• Infections and chronic inflammation can impair red-cell production and restrict the availability of stored iron.
• Malaria and inherited haemoglobin disorders, including thalassaemia and sickle-cell disease, can cause anaemia through mechanisms other than simple dietary iron deficiency.
• Several causes can coexist in the same person, so identifying one nutritional deficit need not explain the entire condition.

Implications for public-health action

The distinction supports cause-sensitive prevention and treatment, rather than assuming that every low haemoglobin result requires iron alone.

• Iron supplementation and food fortification can address iron deficiency, while dietary diversification helps address multiple nutritional deficiencies.
• Anaemia control also requires measures appropriate to local causes, including infection control, indicated deworming, management of blood loss, and care for inherited blood disorders.
• India's Anaemia Mukt Bharat strategy combines iron-folic acid supplementation with other measures, including testing, treatment and attention to non-nutritional causes.
• Programme assessment should distinguish improvements in haemoglobin from improvements in iron status; neither measurement alone fully describes the other.