Potassium
From Gomerpedia
Potassium is an electrolyte symbolized with the letter K. When potassium is low, everyone freaks out; a condition called hypokalemia. When potassium is high, everyone freaks out again; a condition called hyperkalemia. Hyperkalemia can cause life-threatening arrhythmia in both patients (by affecting depolarization) and health care providers (by scaring the bejeezus out of them).
Related Reading
- Sodium