Monitoring glycaemic control in patients with diabetes mellitus

A 73 year old man with obesity and type 2 diabetes mellitus was referred to the diabetes clinic for advice. He had chronic kidney disease stage 3 and chronic anaemia from angiodysplasia of the small intestine. He was on insulin glargine 35 units every night and soluble human insulin 30 units three times daily before main meals. He was referred because of the discrepancy between his high fasting plasma glucose concentrations (16-21 mmol/L) and lower than expected haemoglobin A1c (HbA1c) concentration (49 mmol/mol) (expected with this fasting plasma glucose concentration ~108-140 mmol/mol or 12-15%). Table 1 gives glucose and HbA1c reference intervals. Other selected blood tests were: haemoglobin 106 g/L (reference interval: 125-180), ferritin 315 µg/L (reference interval: 24-250), creatinine 107 µmol/L (reference interval: 59-104), and albumin 32 g/L (reference interval: 35-50).