NCLEX Practice Test 2025 – 400 Free Practice Questions to Pass the Exam

Serum creatinine is a key laboratory value used to assess kidney function because it is a waste product produced from muscle metabolism and is usually filtered out of the blood by the kidneys. When the kidneys are functioning properly, serum creatinine levels remain relatively stable in the blood. However, when kidney function declines, serum creatinine levels can rise, indicating possible renal impairment or damage.

While blood urea nitrogen (BUN) is also used in evaluating kidney function, it can be influenced by factors other than kidney health, such as protein intake and hydration status, making it less specific than serum creatinine. Potassium levels and calcium levels are important in assessing different aspects of health, but they do not directly reflect kidney function. High or low levels of potassium can indicate an imbalance but are not specific markers for evaluating the kidneys themselves. Thus, serum creatinine is the more reliable choice for directly assessing kidney function.