My 94 Year Old Grandfather Received Two Pints Of Blood

My 94 year old grandfather received two pints of blood plus iron (intravenously) yesterday. He had surgery for prostate cancer 6 months ago and his health has deteriorated substantially since then.
His energy levels were at zero a few days ago and yesterday he received the blood and iron and came home last night. My question is can we expect his energy levels to increase substantially today or will it be a few days before we see benefits.
Tony