Type 1 diabetes occurs when a persons immune system attacks their pancreas stopping them producing insulin. The only current treatment is insulin replacement. Recently a new treatment has been found, which delays the onset of type 1 diabetes giving people more years without insulin. This exciting new treatment can only be given to people before they have diabetes symptoms. To date all research into how to find these early cases has been in children. You can detect early cases by testing children for markers of the immune attack called antibodies. Based on the number and type of these antibodies we can predict a child’s future type 1 diabetes risk and if they will benefit from the new treatment. Half of type 1 diabetes develops in adults but we do not know an adults future type 1 diabetes risk if we find antibodies and thus who needs treating. This study aims to answer this question by looking for antibodies in adult blood samples taken over 5 years ago. We will recontact all adults with antibodies in these old samples and some people without (controls) asking for a finger prick sample (taken at home or in hospital) to measure their antibodies and blood glucose level now. We will also ask if they have developed diabetes and their treatment and diabetes type if they have. This study will allow us to screen for antibodies in adults and predict those most likely to develop type 1 diabetes and therefore benefit from new treatments.