What does low potassium look like on an ecg?

Time for a text book: I assume that you have some reason for having access to ecgs for more than just hypokalemia and understand some of ECG terminology. Under those circumstances, it would be worth your investment in an ECG interpretation textbook. Try mariott or chou. Basics are: wider taller p waves, prolonged pr, t flattening or inversion, st depression, u waves, long qt interval, ectopic arrhythmias.

Low T wave: Hypokalemia (low potassium) characteristically creates a low-voltage t-wave and a prominent u-wave on ones ecg; the u-wave can merge with ones t-wave, creating a long qt interval which is associated with cardiac arrhythmias, some of which can be life-threatening.