Non-adherence is defined as: the extent to which a person's behaviour - taking medication, following a diet, and/or executing lifestyle changes, corresponds with agreed recommendations from a health care provider. Non-adherence in chronic cardiometabolic diseases including diabetes is very common and is often the primary reason for treatment failure. This leads to significant excess costs to the health economy through avoidable investigations, treatment escalations, hospital admissions, and disease complications. Methods to diagnose non-adherence have until recently been poor. We have recently developed an objective and robust chemical adherence test to detect the presence of 160 cardiovascular medications in urine using high performance liquid chromatography-tandem mass spectrometry (LC-MS/MS). Chemical adherence testing has not been utilised in people with diabetes, further its relationship with other measures of adherence is unknown. The main aim of this observational study is to compare chemical non-adherence with other commonly used measures of non-adherence in people with diabetes. Chemical testing for non-adherence will be performed using urine provided by 600 patients with poorly controlled diabetes attending primary care recruited over a 15-month period. Participants will also be required to complete a self- reported questionnaire and pharmacy records will be reviewed to ascertain prescription refill rates. The prevalence and metabolic control of non-adherence as diagnosed chemically will be compared with those obtained by pharmacy refill rates and patient self-reported questionnaires. Further, the determinants of non-adherence as ascertained by urine LC-MS/MS analysis will be studied. It is hoped that this innovative study will lead to further larger intervention studies that will change the management of non-adherence in diabetes.