Potassium overdose is frequently seen in patients with renal failure or those on K sparing diuretics. In mild hyperkalemia (serum levels less than 6.5 mEq/l), leads II, V2 and V4 demonstrate tall, tented, symmetrical T waves with a narrow base. The P wave remains normal, as does the QRS complex. With moderate K overdose (6.5 mEq/l - 8.0 mEq/l) the QRS complex broadens and the S wave is widened in leads V3 - V6. This S wave become continuous with the tented T waves and eventually the ST segment disappears. Furthermore the duration of the P wave is increased, while the amplitude is decreased. At K levels greater than 8.0 mEq/l (see below), the P wave duration and PR interval duration both increase, until the P wave eventually disappears entirely. The QRS complex is diffusely broadened and continuous with the tall, tented T wave in all leads.