Final answer:
The electrolyte or basic metabolic panel (BMP) blood test is used to evaluate the balance of sodium and water in the body and urine.
Step-by-step explanation:
In a blood test to evaluate the balance of sodium and water, the electrolyte or basic metabolic panel (BMP) is used. The BMP measures various factors including sodium concentration, which indicates the amount of sodium in the body, and urine sodium, which reflects the excretion of sodium in urine. Sodium and water balance is crucial for maintaining proper cellular function and overall health.