How long can a human being actually last without water? (no thumb of survival bull)?

I obviously know that I managed to survive for more than 3 days without any food or water. I had survived 7 days without food or water until I was sent to a hospital because people were worried of me (I see why). I was at the age of 12 (I'm 17 now), I weighed somewhere in the 80's (I was light for my age and size). In the ambulance I had my finger poked to scan my blood, but there was none coming out like if there were no flow. All that happened during the time without food or water is that I got really dizzy all the time. I also read that a 97 year old women survived 8 days without food or water, being stuck after an earthquake.