- For those with type 2 diabetes: C-peptide >0.2 nmol (1.1-4.4 ng/ml). If c-peptide is abnormal or there is a clinical suspicion of type 1 diabetes, MODY, or LADA, Anti-Islet cell (negative) and Glutamic Acid Decarboxylase (GAD) antibody negative (0.0-1.5 U/ml) will be performed