American Board of Family Medicine (ABFM) Practice Exam 2026 - Free ABFM Practice Questions and Study Guide

In the context of hyperkalemia, the first diagnostic test to consider is an electrocardiogram (EKG). This is because hyperkalemia can significantly affect cardiac function and generate characteristic changes on the EKG, such as peaked T waves, prolonged QRS duration, and eventually may lead to life-threatening arrhythmias.

When a patient presents with hyperkalemia, immediate assessment of the heart’s electrical activity is crucial. The EKG provides essential information about the heart’s potential response to elevated potassium levels and enables timely intervention if acute complications are suspected. Rapid identification of changes on the EKG allows healthcare providers to decide on necessary interventions, including potential treatments like calcium gluconate or insulin and glucose, to stabilize cardiac activity before addressing the underlying cause of hyperkalemia.

Other diagnostic tests, such as a urinalysis, a complete blood count (CBC), or renal ultrasonography, may provide helpful information in the broader workup of hyperkalemia, especially regarding its etiology, but they do not have the immediate relevance that an EKG holds in assessing the risk of cardiac complications associated with elevated potassium levels.