A 70 year old lady presents with generalised weakness and fatigability for 8 months. She had no other complaints, while her medical and surgical histories are unremarkable.

Her FBC is significant for a Hb of 5.4 g/dL, along with a low MCV, MCHC and MCH. Her electrolytes, liver functions, renal functions, and coagulation profiles are normal.

Repeated questioning reveals a history of intermittent tarry colored stools. Initial and repeat upper GI endoscopies are normal, as is a colonoscopy.