Iron Deficiency

Condition

Iron deficiency can result from multiple causes. It can cause fatigue even without a low Hb, or Hb may be low while the patient is asymptomatic — patients may be total-body iron deficient before Hb starts dropping, manifesting as fatigue and weakness. Once iron deficiency has developed, it’s difficult to restore iron stores by dietary intake alone — supplementation is required. Once stores are replenished, increased oral iron intake alone can be enough to maintain them.

Causes:

• Inadequate dietary intake — toddlers/adolescents, vegans, anorexia nervosa.
• Malabsorption — coeliac disease, pernicious anaemia, post- gastrectomy.
• Increased iron requirements — pregnancy, breastfeeding, rapid growth (toddlers/adolescents), menstruation, GI blood loss (see Haematemesis and Melaena, PR Bleeding).

Blood tests

Serum iron levels do not reflect total body iron stores. Serum ferritin is a better measure, but is an acute-phase reactant — iron deficiency may be masked by infection/inflammation (ferritin >100 is unlikely if the patient is truly iron deficient; ferritin is always >100 in anaemia of chronic disease).

MCV — low in iron deficiency, though it falls later than Hb, so may be normal if blood loss is rapid; <70 is essentially only possible in iron deficiency.

Transferrin saturation — low in iron deficiency, but not very sensitive, and affected by volatility of blood iron levels.

Transferrin — low in iron deficiency, but a negative inflammatory marker (rises when other acute-phase markers fall).

Treatment

Iron supplementation — oral or parenteral.

Oral therapy: 100–210mg elemental iron daily. Studies using doses as low as 15mg/day showed the same rate of increase in iron stores (ferritin) as higher doses, with fewer side effects than 50mg or 150mg doses — e.g. Ferrograd-C (105mg) daily. Adding vitamin C 500mg helps absorption and means iron can be taken with food.

Adverse effects: nausea, bloating, constipation, diarrhoea, black stools.

Absorption is reduced by food — take 1 hour before eating (or with vitamin C). Absorption is also reduced by PPIs, H2 antagonists, antacids, and tea — helpful to take iron in the evening if the patient drinks tea (and possibly coffee) in the morning.

Continue treatment until iron stores are replenished and serum ferritin is back to normal.