What is the unit of measurement for potassium levels from a chemistry lab?

Units of Measurement for Potassium in Chemistry Labs

The standard unit of measurement for potassium in chemistry laboratories is milliequivalents per liter (mEq/L) in the United States, while millimoles per liter (mmol/L) is commonly used in many other countries. 1

Standard Units and Reference Ranges

• Potassium is typically reported in milliequivalents per liter (mEq/L) in the United States clinical laboratories 1
• Some laboratories, particularly in other countries, report potassium in millimoles per liter (mmol/L) 1
• For potassium, 1 mEq/L equals 1 mmol/L, making the numerical values identical regardless of which unit is used 2
• Normal reference ranges for serum potassium are typically 3.5-5.0 mEq/L (or 3.5-5.0 mmol/L) 3

Clinical Significance of Potassium Measurements

• Hypokalemia is defined as a serum potassium level less than 3.5 mEq/L 1, 3
• Hyperkalemia is defined as a serum potassium level greater than 5.0 mEq/L 1, 3
• Potassium levels are critical to monitor as both hypokalemia and hyperkalemia can cause significant cardiac conduction disturbances 1

Measurement Considerations

• Serum potassium concentrations are usually 0.1-0.4 mEq/L higher than plasma levels due to potassium release from platelets during coagulation 1
• Hemolysis during blood collection can falsely elevate potassium levels, requiring repeat testing 4
• Point-of-care testing can provide potassium results approximately 35 minutes earlier than central laboratory measurements 5

Clinical Classifications of Potassium Abnormalities

Hypokalemia Classification:

• Mild: 3.0-3.5 mEq/L 1
• Moderate: 2.5-2.9 mEq/L 1
• Severe: <2.5 mEq/L 1

Hyperkalemia Classification:

• Mild: 5.5-6.4 mmol/L (or mEq/L) 1
• Moderate: 6.5-8.0 mmol/L (or mEq/L) 1
• Severe: >8.0 mmol/L (or mEq/L) 1

Important Monitoring Considerations

• Potassium levels should be monitored more frequently in high-risk patients, such as those with heart failure, chronic kidney disease, or diabetes mellitus 1, 6
• For patients on mineralocorticoid receptor antagonists, monitoring is recommended 1 and 4 weeks after initiation/uptitration, then at 8 and 12 weeks, and every 4 months thereafter 1
• Recent evidence suggests maintaining potassium levels ≤5.0 mEq/L may be safer than the traditional upper limit of 5.5 mEq/L, especially in patients with heart failure 6