What Causes Leg Cramping And Body Shaking Uncontrollable?

Leg cramping, often. Body shaking uncontrollably - usually end up at ER and they give fluid (saline) for dehydration and it seems to go away. I drink lots of water and green tea, but my body doesn't seem to retain it; I am a 73 year old male. On no medications. This shaking seems to hit me about every 14 to 16 months and will be present if I get ill like when I had a UTI.