Mr Black is a 69 year old gentleman who has come to see you with ongoing weight loss and diarrhoea. He was seen recently by a colleague who requested urgent endoscopy investigations (both upper and lower gastrointestinal endoscopies are normal). Mr Black informs you that his weight loss has continued (lost 11kg in the last six months) and he has also noticed polyuria and polydipsia. Mr Black is known to have Hypertension and Ischaemic heart disease. He currently smokes 15 cigarettes a day and used to drink heavily in the past. Abdominal examination is grossly unremarkable and observations are within normal limits except a random blood glucose is 13.9.
What is the next most appropriate course of action?