What does a high serum creatinine level typically indicate?

A high serum creatinine level is primarily an indicator of decreased kidney function. Creatinine is a waste product produced from normal muscle metabolism and is typically excreted by the kidneys. When kidney function declines, the ability to filter creatinine from the bloodstream diminishes, leading to elevated serum levels. This makes it a reliable marker for assessing renal function, as high levels suggest that the kidneys are not clearing waste products effectively, potentially indicating issues such as acute kidney injury, chronic kidney disease, or other forms of renal impairment.

In contrast, increased hydration generally leads to lower serum creatinine levels, as more fluid can help dilute the concentration of substances in the blood. While a high protein diet can increase creatinine levels temporarily due to increased muscle metabolism, it is not as definitive an indicator of kidney function as elevated serum creatinine itself. Exercise intensity can also impact creatinine levels through muscle work, but this is typically less significant than the direct effects of kidney function. Thus, decreased kidney function is the most accurate interpretation of a high serum creatinine level.