Which electrolyte imbalance can cause peaked T waves on ECG?

• A. Hypokalemia
• B. Hyperkalemia
• C. Hypercalcemia
• D. Hyponatremia

Answer: (B)

Peaked T waves on an ECG point to elevated potassium levels in the blood. When extracellular potassium rises, the ventricular resting potential becomes less negative, which speeds up repolarization and makes the T wave taller and more pointed. This is one of the earliest ECG signs of hyperkalemia, and as potassium increases further you may see a shortened QT interval, widening of the QRS, and eventually more dangerous rhythms. In contrast, other electrolyte disturbances have different ECG patterns: low potassium tends to cause flattened or inverted T waves with prominent U waves; high calcium shortens the QT interval but doesn’t produce peaked T waves; and low sodium doesn’t have a classic peaked-T wave finding.