My sister has ongoing calcium deficiency and needs to take thousands of milligrams of calcium every day or she will die. If she misses a dose or has a bit of chocolate or caffeine (which interfere with calcium absorbtion) her hands, feet, and mouth start to cramp like that. If she does not take calcium at the first sign, her hands will cramp so she isn't able to use them. If she continues to not take calcium her arms will cramp into her chest and her legs will cramp into her body, and her heart will stop.

Dude, she always has calcium on hand. It's creepy.