It has been shown that close control of blood glucose levels in the intensive care unit patient has benefits for patient morbidity and mortality rates as well as an impact upon discharge times. GlySure has previously completed an evaluation of its intra-vascular glucose monitoring system in patients in a surgical ICU environment after cardiac surgery. This study seeks to evaluate the same equipment being used in a wider range of patients with a range of underlying conditions who require treatment in medical ICU's. The GlySure device consists of a sensor that is placed into the patient's blood through a central venous catheter. It measures blood glucose levels continuously which allows for more rapid control of blood glucose levels to be achieved as compared to existing methods where blood samples are taken repeatedly every 15 minutes or so.