MRCP2-2318

A 54-year-old man with chronic renal failure visited the renal clinic. He was receiving regular haemodialysis and had been taking oral ferrous sulphate (200 mg three times a day) for the past six months. During his clinic visit, his haemoglobin level was found to be 76 g/L, which was significantly lower than the 106 g/L level recorded six months ago. What is the best course of treatment in this case?