Blood become denser when you are dying of deshidration?
Yes blood becomes denser on dehydration (water dilutes the blood, if there's no water in blood it becomes dense). No, body does not draw water from the blood. When you are dehydrated, blood is the first source to be depleted. Then blood pulls water from cells (there are various hormones acting on kidneys and blood vessels trying to preserve the remaining amount of water by increased reabsorption, decreased excretion and vasoconstriction to comparitively useless parts of the body) and on continued dehydration, heart is not getting enough blood to pump as liver is sacrificing all its blood to the brain and cells are being depleted of water and are dried up. So blood is dense and there is not enough amount to reach the brain and brain cells don't get enough glucose (ischemia) and build up of urea and BUN in blood on the other side. Brain Cells switch the metabolism as they try to keep the cells alive only to produce radical oxygen species as by-products which in turn destroys the cells. And hence. Death. Eventually.