why we get thirsty?

Thirst is a sensation indicating the body's need for water. It is a natural feeling that we all get when the fluid level in our body is reduced. Our body is 75 percent water so we need it as we lose it .

When you lose water from the body in the form of sweat or urine,  your body needs water.  When it reaches low, the body signals the brain to drink to replenish lost water in the body. Normal thirst is caused by concentrared blood.