I have that problem, mostly in my feet. I've had it for a few months now. Originally I went to my doctor and he told me to take epsom salt baths and take calcium supplements. He tested for electrolytes and vitamin deficiencies and didn't find anything.

However, my understanding is that people with MG shouldn't supplement magnesium (which is the active ingredient in epsom salts) and I really wouldn't supplement at all without asking your doctor.

I do roll my cramps with a rolling pin or a tennis ball sometimes. I can't really say that it helps although people keep assuring me that it will. I'll be following to read the other responses.