Final answer:
The nurse should monitor for decreased serum levels of potassium when patients are receiving loop and thiazide diuretics.
Step-by-step explanation:
When monitoring laboratory test results for patients receiving loop and thiazide diuretics, the nurse should look for a. decreased serum levels of potassium. Loop and thiazide diuretics work by increasing urine production, which can lead to the loss of potassium from the body. Therefore, it is important to monitor potassium levels in patients taking these medications.