text: I have had 1 after an episode where I lost a large amount of blood...it only took me about 3 days to feel normal again.  My mother had cancer and received 2, and she felt better within 24 hours.  It depends on the reason you are having one. She was going through chemo and became anemic.  She was very weak and dizzy, kept trying to pass out and could barely stand on her own feet, let alone walk. So it was amazing to see the difference by the next day when she was able to walk without feeling weak and dizzy.  I hope this helps.