A fit elderly gentleman, around 75 years old, with background of hypertension, type 2 diabetes mellitus, hypercholesterolaemia, Ischaemic heart disease, was referred by his GP for investigation of his iron deficiency anaemia. He did complainted of some chronic constipation for many years, which was not a new symptoms for him. He denied any malaena or fresh PR bleeding. He denied any upper gastrointestinal symptoms. He was a fit and healthy elderly gentleman, still driving around with his car. He did have a well balanced diet. Initally, OGD and Colonoscopy were done on him, which were normal. No contributory causes for iron deficiency ananemia found on the endoscopy investigation. What will be your next step of management or investigation ?? Do we need to do any further investigation for his iron deficiency anaemia ??