Neutrophil gelatinase-associated lipocalin (NGAL) is a novel early marker of acute kidney injury (AKI) for which it has been shown that it can also be released from the injured myocardium. It is a small protein expressed in neutrophils and in low levels in the kidney, prostate, and epithelia of the respiratory and alimentary tracts.

Under normal conditions NGAL levels are low in urine and plasma but rise sharply within 2 hours from basal levels in response to kidney injury to reach diagnostic levels within a very short time - as much as 24 hours or more before any significant rise in serum creatinine. 

Because NGAL is protease resistant and small, the protein is easily excreted and detected in the urine. NGAL levels in patients with AKI have been associated with the severity of their prognosis and can be used as a biomarker for AKI. NGAL can also be used as an early diagnosis for procedures such aschronic kidney disease, contrast induced nephropathy, and kidney transplant.