Type 1 diabetes (T1D) is a chronic condition, affecting 1 in 490 children under the age of 15 years. It is caused by the immune system damaging the pancreas, the organ which makes insulin. T1D has recognised stages before symptoms develop, providing an opportunity for early diagnosis, education and treatment which may delay the onset of symptoms. Early diagnosis often relies on a test called the oral glucose tolerance test (OGTT), which is commonly used but not well tolerated, possibly because it requires a drip inserted into the vein, and several blood samples taken over 2-3 hours in a healthcare setting. This study aims to test whether an OGTT using a finger-prick to test glucose, can be done at home. This is the 'GTT@home'. The finger-prick creates a drop of blood, which is done before and two hours after drinking a sugary drink. Investigators will also explore whether a continuous glucose monitor (CGM), which reads glucose levels through the skin could be an alternative. The investigators plan to recruit 90 children and young people, across two groups to assess the GTT@home. To understand the experiences of those involved in monitoring, the investigators will invite young people, parents and healthcare workers to take part in an interview, to understand the impact of testing to predict clinical T1D. Group 1 will assess the accuracy of measuring glucose from a finger-prick blood test when compared to a blood test from the vein. The investigators will recruit individuals who are having an OGTT as part of a research study, for clinical care, or if individuals have agreed to have an OGTT for this study. Those with T1D will be invited to wear a CGM to explore its use as an additional, practical alternative. Group 2 will assess how well the GTT@home test works when done at home and how acceptable it is. This will only be offered to those known to be at risk of T1D. These studies will help investigators to understand if the GTT@home can be used in routine care.