His current research encompasses three areas:

First, development of a new model of early diabetic nephropathy.  In large follow-up studies of Joslin Clinic patients, he discovered a new stage of diabetic nephropathy. His discovery changed the established paradigm of early nephropathy, creating a new model that highlights early progressive renal decline, instead of the previously emphasized microalbuminuria, as the primary stage of diabetic nephropathy to be diagnosed and treated to reduce risk of end-stage renal disease.

Second, search for biomarkers of progressive renal decline. Using biobanks of specimens established in his multiple follow-up studies, he examines blood and urinary profiles of proteins, metabolites and microRNAS that are associated with risk of renal decline. This research aims to discover new therapeutic targets to prevent/treat renal decline and find prognostic biomarkers to identify patients at risk of renal function loss. One discovery so far is that high serum uric acid concentration is a determinant of early renal decline. This led to the PERL multi-center clinical trial that tests whether lowering serum uric acid can reduce the rate of renal decline. Another discovery is that elevated serum concentrations of TNFR1 is a strong independent predictor of early and late renal decline. The test based on this discovery will soon be available in clinical practice.

Third, search for susceptibility genes for nephropathy. Dr. Krolewski is the leader in research on genetics of diabetic nephropathy. As one of the PIs of the multination JDRF Collaborative Research Initiative on Genetics of Diabetic Nephropathy, he leads the effort to identify genes that specifically increase the risk of progressive renal decline leading to end-stage renal disease.