Potassium (K)
Complete guide to potassium blood testing — normal ranges, causes of high and low potassium, and when to get tested.
What is Potassium?
Potassium is an essential electrolyte primarily found inside your cells. It's crucial for heart function, nerve signaling, and muscle contractions.
Why is it Important?
Potassium is vital for:
- Maintaining normal heart rhythm
- Regulating muscle contractions
- Supporting nerve function
- Balancing fluids and pH in the body
Abnormal potassium levels can cause dangerous heart rhythm problems and muscle weakness.
Normal Ranges
| Group | Range | Unit |
|---|---|---|
| Adult | 3.5 – 5.0 | mEq/L |
| Critical Low | < 2.5 | mEq/L |
| Critical High | > 6.5 | mEq/L |
What Do Abnormal Results Mean?
Low Potassium (Hypokalemia)
Common causes include:
- Diuretic medications
- Excessive vomiting or diarrhea
- Laxative abuse
- Low dietary potassium
- Hyperaldosteronism
- Magnesium deficiency
High Potassium (Hyperkalemia)
Common causes include:
- Kidney disease or failure
- ACE inhibitors or ARB medications
- Potassium-sparing diuretics
- Addison's disease
- Severe tissue breakdown (rhabdomyolysis)
- Hemolyzed blood sample (false elevation)
When Should You Get Tested?
Potassium is measured in routine metabolic panels. Your doctor may order it if you're taking diuretics or heart medications, have kidney disease, or experience symptoms like muscle weakness, cramping, irregular heartbeat, or fatigue.
This information is for educational purposes only and is not a substitute for professional medical advice.
Last reviewed: 2026-02-13