From the Guidelines
Low potassium (hypokalemia) is a condition characterized by serum potassium levels less than the laboratory lower limit of normal, with severity classified as mild (<3.5 to ≥3.0 mEq/L), moderate (<3.0 to ≥2.5 mEq/L), and severe (<2.5 mEq/L) 1.
Symptoms and Signs
The symptoms and signs of low potassium include:
- Muscle weakness
- Fatigue
- Muscle cramps
- Constipation
- Heart palpitations In severe cases, patients may experience:
- Paralysis
- Respiratory failure
- Dangerous heart rhythm abnormalities
Physical Examination and Diagnostic Findings
Physical examination might reveal:
- Decreased deep tendon reflexes
- Irregular heartbeat
- Low blood pressure An electrocardiogram (ECG) typically shows characteristic changes including:
- Flattened T waves
- Prominent U waves
- ST segment depression
Treatment and Management
Treatment depends on the severity of hypokalemia, but often includes:
- Oral potassium supplements like potassium chloride tablets (typically 20-40 mEq daily in divided doses) for mild cases
- Intravenous potassium at rates not exceeding 10-20 mEq per hour for severe or symptomatic cases The underlying cause, such as diuretic use, vomiting, diarrhea, or kidney disorders, must also be addressed 1.
Importance of Potassium
Potassium is crucial for proper nerve and muscle function, particularly for maintaining normal heart rhythm, which explains why cardiac symptoms are prominent in hypokalemia.
From the FDA Drug Label
Potassium depletion may produce weakness, fatigue, disturbances or cardiac rhythm (primarily ectopic beats), prominent U-waves in the electrocardiogram, and in advanced cases, flaccid paralysis and/or impaired ability to concentrate urine. The symptoms and signs of low potassium levels include:
- Weakness
- Fatigue
- Disturbances in cardiac rhythm, primarily ectopic beats
- Prominent U-waves in the electrocardiogram
- In advanced cases, flaccid paralysis and/or impaired ability to concentrate urine 2
From the Research
Symptoms and Signs of Low Potassium
- Muscle weakness or fatigue 3, 4
- Muscle cramps or spasms 5, 6
- Palpitations or irregular heartbeat 7
- Constipation 3
- Fatigue or weakness 4, 6
Treatment and Management
- Potassium supplements 3, 5, 6
- Potassium-sparing diuretics such as spironolactone or triamterene 3, 5, 6
- Aldosterone blockers such as eplerenone 4
- Proton pump inhibitors may also affect serum potassium levels 7
Laboratory Findings
- Low serum potassium levels (< 3.5 mmol/L) 3, 4, 5, 6, 7
- Electrocardiogram (ECG) changes such as flattened T waves, U waves, or QT interval prolongation 3, 7
Special Considerations
- Patients with Gitelman's syndrome may require special consideration and treatment with aldosterone blockers such as eplerenone 4
- Patients taking thiazide diuretics may require potassium supplements or potassium-sparing diuretics to prevent hypokalemia 5, 6
- Proton pump inhibitor use may be associated with higher serum potassium levels 7