... on Interferon and Ribavarin for 11 months w/o success. It was a complete nightmare. Has anybody with brain fog had any improvement with Harvoni tx. and if so how long did it take? I'm already feeling better mentally and physically, just extremely tired. Please let me hear from you. Thank you! I have a lot of faith and hope. I have had Hep C for 25-30 years and cyrrhosis for the past 3 years. My memory is extremely bad and I have been really sick the last year. I will be on Harvoni for 6 months. How long does it usually take to feel back to normal? Does it start getting better before you are done with treatment?