Hi, saw this out on the main page. Severe cramps in the calves, shins and feet are quite common to transplant patients. My Mg was always borderline following my transplant but they kept me topped off. Same with my K. It could be that the supplements were failing at night but i got my cramps often shortly after having a bag of IV Mg.
Thing is, I'm almost 10 years out and I still have those cramps threaten me occasionally (I mean I can feel things tighten up and it feels like they're about to cramp but they don't_. So since my body chemistry isn't being battered anymore, there's something else afoot (no pun intended). I use medical marijuana and noticed my cramps went away shortly after I use it. I can't say that MMJ will help you but if you live in a state that allows it, you might give it a try.
Blessings