What is a common laboratory test performed on a specimen from a patient taking furosemide (Lasix)?

Furosemide, commonly known by the brand name Lasix, is a diuretic medication frequently prescribed to help reduce fluid overload in patients with conditions such as heart failure or edema. One of the critical effects of furosemide is its impact on electrolyte balance, particularly through increased urine output.

When a patient is on furosemide, monitoring potassium levels becomes essential. This is because furosemide can lead to potassium depletion (hypokalemia) as it causes the kidneys to eliminate more potassium along with excess fluid. This makes the assessment of potassium levels a routine laboratory test in these patients. An abnormal potassium level can have significant clinical implications, including potential cardiac issues, so it is critical for healthcare providers to be aware of and manage electrolyte status in patients on diuretics.

While other electrolyte tests like calcium, sodium, and magnesium can also be important, the direct and frequent association of furosemide with potassium imbalances makes potassium level monitoring a common and necessary laboratory test for patients taking this medication.