What does an abnormal nitrite level most commonly indicate?

An abnormal nitrite level in urine most commonly indicates a urinary tract infection (UTI). The presence of nitrites occurs when bacteria that reduce nitrate to nitrite are present in the urinary system, which typically indicates a bacterial infection. Many common UTI-causing bacteria, such as Escherichia coli, produce enzymes that convert nitrates, found naturally in urine, into nitrites.

In contrast, conditions like glomerulonephritis, normal kidney function, or kidney stones do not typically affect nitrite levels in the urine. For example, glomerulonephritis involves inflammation of the kidney's filtering units and may show different markers in urine such as protein or blood, but not usually nitrites. Normal kidney function would indicate that there are no abnormalities present, and kidney stones primarily cause pain and may lead to hematuria (blood in urine) but do not influence nitrite levels. Thus, when nitrites are detected in urine, it is a strong indication of a UTI.