True or False? Serum creatinine levels may be falsely elevated when a patient is taking cephalosporin.

• A. True
• B. False
• C. Cannot be determined
• D. Not affected

Answer: (A)

The measurement of serum creatinine commonly relies on a colorimetric reaction that is not perfectly specific. Cephalosporin antibiotics can interfere with this assay by reacting in the same chemical environment or altering the reaction in a way that produces a color signal similar to that of creatinine. This interference makes the test read higher than the true creatinine concentration, giving a falsely elevated result. Because of this, a patient taking cephalosporins may show an apparently higher creatinine even if kidney function is normal. If accuracy is essential, laboratories can use enzymatic creatinine assays or alternative methods that are not affected by cephalosporins, ensuring the result reflects true renal function.