Potassium normal ranges
Reading File
Finding Sources
Searching the Web
serum potassium normal range reference values clinical
Here is a complete reference for potassium normal ranges:
Serum Potassium - Normal Reference Ranges
Adults
| Measurement | Normal Range |
|---|---|
| Serum potassium | 3.5 - 5.0 mEq/L (most labs) |
| Some lab references | 3.5 - 5.2 mEq/L |
mEq/L = mmol/L for potassium (they are numerically identical)
By Age Group (RCPA Reference Ranges)
| Age | Normal Range |
|---|---|
| Newborn (0 - <1 week) | 3.8 - 6.5 mmol/L |
| Infant (1 week - <26 weeks) | 4.2 - 6.7 mmol/L |
| Infant/toddler (26 weeks - <2 years) | 3.9 - 5.6 mmol/L |
| Child/adolescent (2 - <18 years) | 3.6 - 5.3 mmol/L |
| Adult (18+) | 3.5 - 5.2 mmol/L |
Note: Infants and neonates normally have higher potassium than adults.
Clinical Interpretation
| Value | Classification |
|---|---|
| < 3.5 mEq/L | Hypokalemia |
| 3.5 - 5.0 mEq/L | Normal |
| > 5.0 mEq/L | Hyperkalemia |
Clinically significant thresholds:
- Severe hypokalemia: < 2.5 mEq/L (cardiac arrhythmia risk)
- Mild hypokalemia: 3.0 - 3.5 mEq/L
- Mild hyperkalemia: 5.0 - 5.5 mEq/L
- Severe hyperkalemia: > 6.5 mEq/L (life-threatening, immediate ECG changes)
Urine Potassium (Spot Sample)
| Value | Interpretation |
|---|---|
| < 20 mEq/L | Suggests poor intake, GI loss, or intracellular shift |
| > 40 mEq/L | Suggests renal potassium wasting |
Key Points
- Serum vs plasma: Serum values run ~0.1-0.5 mEq/L higher than plasma due to release from platelets during clotting - this is a known pre-analytic artifact.
- Pseudohyperkalemia (falsely elevated) can occur with hemolysis, prolonged tourniquet use, or extreme leukocytosis/thrombocytosis.
- Hypertension patients: Recent evidence suggests an optimal range of 4.1 - 4.7 mmol/L is associated with lowest mortality, narrower than the standard reference range.
- The normal range may vary slightly between laboratories - always check your lab's specific reference interval.
Sources: Goldman-Cecil Medicine; Schwartz's Principles of Surgery; RCPA Manual; Medscape Reference
This is a shared conversation. Sign in to Orris to start your own chat.