What causes leg cramps in the middle of the night, and what can i do to prevent them?

Many possibilities: Restless leg syndrome usually causes such symptoms in the evening and bedtime. Poor circulation has to be considered. Certain medications, low potassium levels, other conditions as well should be considered. Talk to your internist or sleep physician.

Many reasons: Exertion, standing on feet for long hours, medications like water pills, dehydration like in sports, and electrolyte changes in the blood e.g. Sodium and potassium could be the cause. If you do not have recent blood work within several months, you need one. Check with your doctor and make sure you report activity level, medications. A pickle at bedtime works.Don't use if have CHF or swelling of leg.

Could be veins: Venous insufficiency and varicose veins is a very common cause of leg cramps. If you have trouble with leg cramps and have veins you can see in your legs, i would recommend seeing a phlebologist (vein specialist).