Table 4. Reasons for failure to respond to oral iron therapy .

Reason	Example
Inadequate iron intake	Non-adherence, insufficient iron content in supplement
Inadequate iron absorption	Concomitant consumption of inhibitors of iron absorption (e.g. tea, calcium) Coexisting inflammation with iron sequestration Intestinal mucosal disorders (e.g. coeliac disease) Helicobacter pylori infection Impaired gastric acid secretion (use of proton pump inhibitors)
Ongoing blood losses	Occult blood loss
Coexisting condition interfering with bone marrow response	Concomitant vitamin B12 or folate deficiency, primary bone marrow disease
Incorrect diagnosis	Haemoglobinopathy, anaemia of chronic disease or renal failure