Diabetes Genes

C-peptide and Islet autoantibody testing


C-peptide is a measure of how much insulin a person is making themselves.  As Type 1 diabetes is associated with severe insulin deficiency, low levels of C-peptide are indicative of Type 1 diabetes.  C-peptide can be measured in plasma or in urine.  For further information on C-peptide testing, please follow these links:

Plasma: https://www.exeterlaboratory.com/test/c-peptide-plasma/

Urine: https://www.exeterlaboratory.com/test/c-peptide-urine/



Islet autoantibody tests:

Islet autoantibodies are markers of the autoimmune process associated with Type 1 diabetes.  There are 3 main antibodies that can be tested clinically to inform whether a person is likely to have Type 1 diabetes: GAD, IA2 and ZnT8.  For further information on testing for these antibodies please click on the links below:

GAD: https://www.exeterlaboratory.com/test/gad-antibodies/

IA2: http://www.exeterlaboratory.com/ia-2-ia2-antibodies/

ZnT8: http://www.exeterlaboratory.com/test/zinc-transporter-8-znt8-islet-autoantibodies/


Close to diagnosis (within 3 years) islet autoantibody tests (GADA, IA2 and/or Znt8) are the most appropriate biomarker test for diagnosing diabetes subtypes. C-peptide may be relatively preserved at diagnosis of type 1 diabetes, particularly in the presence of obesity (insulin resistance), so while a low result may confirm type 1 diabetes a high result close to diagnosis is usually unhelpful. In long duration diabetes C-peptide is the most appropriate diagnostic test, as it is loss of endogenous insulin secretion that defines the glycaemic treatment requirements of Type 1 and Type 2 diabetes.