When you are getting cramps in your calves at night, the immediate response from the medical establishment is that you are lacking potassium and the cramps are the result of some systemic deficiency. Well I would like to suggest an alternative explanation as to why this may be occurring. Could it be that the calf cramps are the result of sciatica?
The sciatic nerve innervates the hamstrings (posterior thigh muscles) and every muscle below the knee including the calves. If the sciatic nerve is impinged by a strained piriformis muscle (a muscle in the gluteal region that sits very close to the sciatic nerve), this will cause hyperstimulation of the nerve which can cause excessive nerve supply to the calves causing them to go into spasm and cramp. Clearly based on this information anyone would agree that this is a rational explanation as to why someone may experience cramps in their calves.
In order to come to the resolution of the cramping one must first resolve the training of the piriformis muscle by reinforcing the muscles that work in conjunction with the piriformis muscle; sometimes the glute med, glute max and the hamstrings. By doing this one will prevent the piriformis from training, thickening and extremely impinging on the sciatic nerve creating hyperstimulation of the calf muscles.
You need to perform hamstring curls, straight leg dead lifts and hip abduction to strengthen the appropriate muscles. If taking potassium is not resolving your calf cramping at night, this might be the answer to a good night's sleep.