Hypokalemic Periodic Paralysis = HKPP = A rare genetic disorder that causes potassium to shift into the cells (not out of the body).
Surprise! With HKPP, the potassium level doesn't HAVE to shift out of the normal range to cause weakness or paralysis--it is the relative downward SHIFT that causes the muscle cell membranes to depolarize. I have HKPP and have been virtually paralyzed (very weak, unable to walk, hard to breath) by a drop from 4.2 to 3.6 (with low normal at 3.5).
There is a fairly good test for HKPP called a CMAP or Compound Muscle Amplitude Potential test. It is very safe and about 90% accurate. Do NOT let anyone give you an insulin/glucose challenge to test for HKPP. If you actually DO Have HKPP, the insulin/glucose challenge could KILL YOU! Trust me on this one, your doctor will NOT be prepared for the type of nasty paralysis this test can cause. Don't risk it when the CMAP is easier, safer and more accurate.