Here are the main reasons you may be getting leg cramps at night. These are based on my own personal experience as well as treating hundreds of patients with this issue. For most of us, it's so easy to manage. Yes, really. Number one (by far!) - Not drinking enough water during the day. You need to adjust how much water you drink for your activity level. Even low activity days should take into account that we lose about 2 cups of moisture each day just from breathing. #2