Michael R. Rickels, Peter G. Stock, Eelco J. P. de Koning, Lorenzo Piemonti, Johann Pratschke, Rodolfo Alejandro, Melena D. Bellin, Thierry Berney, Pratik Choudhary, Paul R. Johnson, Raja Kandaswamy, Thomas W. H. Kay, Bart Keymeulen, Yogish C. Kudva, Esther Latres, Robert M. Langer, Roger Lehmann, Barbara Ludwig, James F. Markmann, Marjana Marinac, Jon S. Odorico, François Pattou, Peter A. Senior, James A. M. Shaw, Marie‐Christine Vantyghem, Steven White

β-cell replacement therapy, available currently as pancreas or islet transplantation, has developed without a clear definition of graft functional and clinical outcomes. The International Pancreas & Islet Transplant Association (IPITA) and European Pancreas & Islet Transplantation Association (EPITA) held a workshop to develop consensus for an IPITA/EPITA Statement on the definition of function and failure of current and future forms of β-cell replacement therapy. There was consensus that β-cell replacement therapy could be considered as a treatment for β-cell failure, regardless of etiology and without requiring undetectable C-peptide, accompanied by glycemic instability with either problematic hypoglycemia or hyperglycemia. Glycemic control should be assessed at a minimum by glycated hemoglobin (HbA1c) and the occurrence of severe hypoglycemia. Optimal β-cell graft function is defined by near-normal glycemic control (HbA1c≤6.5% [48 mmol/mol]) without severe hypoglycemia or requirement for insulin or other antihyperglycemic therapy, and with an increase over pre-transplant measurement of C-peptide. Good β-cell graft function requires HbA1c<7.0% (53 mmol/mol) without severe hypoglycemia and with a significant (>50%) reduction in insulin requirements and restoration of clinically significant C-peptide production. Marginal β-cell graft function is defined by failure to achieve HbA1c<7.0% (53 mmol/mol), the occurrence of any severe hypoglycemia, or less than 50% reduction in insulin requirements when there is restoration of clinically significant C-peptide production documented by improvement in hypoglycemia awareness/severity, or glycemic variability/lability. This article is protected by copyright. All rights reserved.