The nurse is monitoring the client's serum electrolytes. Which of the client's serum laboratory values requires intervention by the nurse?
1) Digoxin 2.0 ng/mL (2.56 nmol/L)
2) Sodium 135 mEq/L (135 mmol/L)
3) Potassium 3.0 mEq/L (3.0 mmol/L)
4) Calcium 8.72 mg/dL (2.18 mmol/L)