Erect... dysfunction and Dehydration can reduce blood volume, which means the body has less blood circulating throughout the system. Proper blood flow to the penis is essential for an erection, and when there is insufficient blood flow, it can become more difficult to achieve or maintain an erection. Dehydration can affect the balance of hormones in the body, including those involved in sexual health. For instance, it can influence testosterone levels, which play a key role in sexual desire and function.