Type 1 diabetes (T1D) results from destruction of insulin producing beta cells by the body's own immune system (autoimmunity) causing an individual to lose the ability to make enough insulin to control their blood sugar levels and need to have insulin injections to lower blood glucose levels. Whilst high blood sugar level is a problem for people with Type 1 diabetes, taking insulin medication to lower sugar levels, delayed meals and exercise can all result in dangerously low blood sugar levels (hypoglycaemia). The biological causes of hypoglycaemia, and ways to prevent it are poorly understood. In non-diabetic individuals, a hormone called glucagon is secreted naturally to raise blood glucose levels but it is unclear why glucagon secretion is impaired during hypoglycaemia in individuals with T1D. The aim of this prospective observational study is to test the relationship between a glucagon stimulation test and risk of hypoglycaemia in T1D. It is hoped this research will establish whether this relationship could be used as a blood test and be a clinically useful biomarker of hypoglycaemia risk and, therefore, directly inform clinical care of people with T1D, particularly those with highest risk of hypoglycaemia. Assessment of beta cell decline has traditionally relied on timed C-peptide measures following a standardised liquid meal known as the mixed meal tolerance test (MMTT). Home finger prick blood spot C-peptide measurement might be a practical, cheap, and non-invasive alternative to a MMTT and would allow regular assessment of beta cell function over time. If proven that this sample type is a robust alternative to the gold standard MMTT venous C-peptide, it would dramatically decrease the cost and participant burden of T1D research into beta cell function.