What Is Potassium in a Blood Test?

Potassium regulates heartbeat, nerve signals, and muscle contraction. Even small deviations can be dangerous.

Normal Range

• 3.5–5.1 mEq/L
• Hyperkalemia: above 5.5 mEq/L — potentially life-threatening
• Hypokalemia: below 3.5 mEq/L
• Severe hyperkalemia: above 6.5 mEq/L — medical emergency

High Potassium Causes

• Kidney disease
• Medications — ACE inhibitors, ARBs, potassium-sparing diuretics
• Adrenal insufficiency
• Tissue breakdown
• Lab artifact — hemolyzed sample (most common cause of mild elevation)

Low Potassium Causes

• Diuretics
• Vomiting or diarrhea
• Hyperaldosteronism
• Magnesium deficiency

Why It Matters

• Heart is extremely sensitive to potassium
• High = arrhythmia, cardiac arrest risk
• Low = weakness, cramps, arrhythmia
• Part of BMP and CMP panels