Cramps when you stretch your legs in bed may be caused by calcium deficiency, cold and excessive exercise, etc. Depending on the situation, there are different treatments, such as taking oral calcium and vitamin D3, emphasizing on keeping warm and paying attention to exercise. It is recommended to adjust or treat accordingly under the guidance of an experienced doctor. The most common cause of leg cramps in sleep is low blood calcium caused by calcium deficiency in the body, which will lead to involuntary muscle twitching. Patients can take oral calcium and vitamin D3 for treatment. Cramps can also occur when the leg muscles are irritated by cold at night. It is important to keep the legs warm at night. Muscle fatigue due to over-exercise can also cause cramps in bed. This can be avoided by warming up before exercising and by gradually increasing the intensity of the exercise.