How do kidneys conserve water?

Kidneys conserve water primarily through the process of concentrating urine. This is achieved in the nephron, particularly in the loop of Henle and the collecting duct, where water is reabsorbed back into the bloodstream in response to the hormone vasopressin (also known as antidiuretic hormone, ADH). When the body is dehydrated, higher levels of ADH are released, promoting greater water reabsorption and producing more concentrated urine. Additionally, the kidneys adjust the reabsorption of sodium, which also influences water retention.