# A client taking furosemide reports muscle weakness and irregular heartbeats. Which laboratory value should the nurse check first?

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> url: https://mymerci.kr/pages/nclex_q.php?qn_id=394139&lang=en  
> language: en  
> subject: Adverse Effects/Contraindications/Interactions  
> category: PPT

## Question

A client taking furosemide reports muscle weakness and irregular heartbeats. Which laboratory value should the nurse check first?

## Option

1. Hemoglobin
2. Serum calcium
3. Platelet count
4. Serum potassium **✔ Correct answer**

**Correct answer: 4**

## Explanation

Furosemide is a loop diuretic that can cause potassium loss. Muscle weakness and irregular heartbeats may indicate hypokalemia, which can lead to dysrhythmias. Serum potassium is the priority laboratory value to check.

## In-depth explanation

Clinical Judgment
Loop diuretic symptoms often point toward electrolyte loss.

Memory Tip
Furosemide flushes potassium.

## Clinical scenario

Clinical Practice Guide
Loop diuretic monitoring includes weight, intake/output, blood pressure, renal function, and electrolytes including potassium.

Caution
Irregular heartbeat with possible hypokalemia needs prompt assessment.

## Key concepts

- **Furosemide** — A loop diuretic used to remove excess fluid.
- **Hypokalemia** — Low serum potassium that can cause weakness and dysrhythmias.
- **Loop Diuretic** — A diuretic class that increases urine output and electrolyte loss.

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