Calf cramps in the middle of the night may be caused by overwork during the day, lack of calcium, cold and other reasons. 1. Overwork during the day: If you stand or walk for a long time during the day, your leg muscles will be overworked, causing an abnormal accumulation of lactic acid in the muscles and spasms, which may lead to the symptoms of calf cramps in the middle of the night. 2. Calcium deficiency: when there is an abnormal loss of calcium ions in the body, so that the concentration of calcium ions in the blood is lowered, unable to inhibit the excitability of the muscle nerves, the muscle tissue is too excited, it will cause abnormal muscle spasms, which will be manifested as the symptoms of calf cramps in the middle of the night. 3. Catching cold: when you sleep at night, you do not cover the quilt in the middle of the night, so that your calves are stimulated by the cold air outside, which will make the local muscles have abnormal spasms, thus leading to the symptoms of calf cramps in the middle of the night. Caused by more causes of calf cramps in the middle of the night, if there are uncomfortable symptoms, it is recommended to go to the hospital in time for examination, clear causes, under the guidance of a professional physician, combined with their own physical condition targeted treatment, to avoid the impact on the health of the body.