End-stage renal disease (ESRD) patients have been associated with accelerated vascular disease of the cerebral circulation due to uremic toxins. Furthermore, anemia increases cerebral oxygen extraction fraction which impairs the cerebral vasodilatory capacity. We evaluated the effect of correction of anemia on cerebral blood flow by measuring the mean blood flow velocity, resistance index (RI), and pulsatility index (PI) in the middle cerebral artery (MCA) in relation to cognitive functions. We measured the mean blood flow velocity, RI, and PI in MCA of 120 ESRD patients when the hemoglobin (Hb) ranges between 8 and 10 g/dL and after correction of anemia to two Hb ranges between 10-11.5 g/dL and 11.5-12.5 g/dL in the same patients using transcranial Doppler (TCD) ultrasound in relation to cognitive functions assessment by Mini-Mental State Examination. We observed that there is a mild-to-moderate cognitive impairment in hemodialysis (HD) patients associated with anemia. With the improvement of anemia, the cognitive functions improved. There was an improvement of blood flow of MCA with improvement of Hb. The improvement was obvious at Stage 3 (Hb 11.5-≤12.5 g/dL) in comparison to Stage 2 (Hb 10-<11.5 g/dL) with P <0.001 at all. The optimal Hb for HD patients ranges from 11.5 to ≤12.5 g/dL which associated with better improvement of cognitive function and cerebral circulation investigated by TCD ultrasound for MCA.