No warning msg does NOT mean that your drink and food is at max. I read somewhere that you get no warning message if your drink is 2000+ and your food is 600+. But to regenerate blood you need drink 3000+ and food 2500+. I can tell you for a fact that regeneration works. I had black and white and super blurred vision and I stuffed my stomache (you get a message when you eat A LOT). Then I started to regenerate blood. So after you get no "thirst" "hunger" in character screen you need to eat like 5 more whole cans of food (I dont know the exact amount) until it says you feel full.