Stephen did you ever take lithium? That WILL cause what you are experiencing. It can happen long after you are not taking the drug anymore. Even decades later, people’s kidneys fail. Muscle cramping (Charlie horses in any muscle including toes and fingers) are a sign that you could be headed for trouble. Get a renal panel done and READ IT, ask about creatinine level specifically. Oh, read my upcoming book, too. I talk a lot about that, discuss potassium at length.