Your body is making more red blood cells to off set the thinner air. This also leads to dehydration. Everyone is different but it makes my body two weeks to full acclimate. During this time it’s easy to get dehydrated. Same goes when people fly. Fly on a long flight and you’re “jet lagged” when you arrive like most people think? They are just actually super dehydrated but don’t know it. Makes you feel tired and super shitty. They need to drink water!