Leg cramps at night may be caused by cold, calcium deficiency, strenuous exercise, vascular disease and so on. 1. Cold: If you don’t pay attention to keep your legs warm when you sleep at night, it may lead to leg muscle spasm after getting cold, which leads to leg cramps at night. 2. Calcium deficiency: usually more common in teenagers, pregnant women and the elderly, mainly due to the lack of calcium ions in the blood, muscle stress will increase, which may lead to night leg cramps. 3. Strenuous exercise: usually after strenuous exercise, because the leg muscles are not well relaxed, in a tense state, easy to lead to leg cramps at night. 4. Vascular diseases: such as varicose veins in the lower limbs or deep vein thrombosis, etc., may affect the blood flow back to the legs, which may lead to leg cramps at night. There may be other reasons for nighttime leg cramps, so it is recommended to consult a doctor in time to clarify the cause of the problem and then carry out standardized treatment.