A hybrid open and closed loop diabetes management apparatus comprising: a sensor providing measurements of glucose level in a human or animal; an insulin pump for delivering a dose of insulin to said human or animal; and a processor which is adapted to perform the following steps: receive said measurements of glucose level from said sensor; calculate an insulin dose to be delivered by said insulin pump based on said received measurement; assess the validity of the status of the apparatus; and send a command to said insulin pump to deliver said calculated insulin dose, dependent on said assessing step confirming that the status is valid, wherein said apparatus is configured to operate in open-loop mode wherein said insulin pump is configured to deliver a preset dose of insulin unless said processor sends a command to said insulin pump so that said apparatus is configured to operate in closed-loop mode and wherein a said command sent to said insulin pump is valid only for a predetermined time interval so that if no further commands are sent to said insulin pump during said predetermined time interval, said insulin pump reverts to said open-loop mode delivering said preset dose of insulin at the end of said predetermined time interval. a sensor providing measurements of glucose level in a human or animal; an insulin pump for delivering a dose of insulin to said human or animal; and a processor which is adapted to perform the following steps: receive said measurements of glucose level from said sensor; calculate an insulin dose to be delivered by said insulin pump based on said received measurement; assess the validity of the status of the apparatus; and send a command to said insulin pump to deliver said calculated insulin dose, dependent on said assessing step confirming that the status is valid, wherein said apparatus is configured to operate in open-loop mode wherein said insulin pump is configured to deliver a preset dose of insulin unless said processor sends a command to said insulin pump so that said apparatus is configured to operate in closed-loop mode and wherein a said command sent to said insulin pump is valid only for a predetermined time interval so that if no further commands are sent to said insulin pump during said predetermined time interval, said insulin pump reverts to said open-loop mode delivering said preset dose of insulin at the end of said predetermined time interval. receive said measurements of glucose level from said sensor; calculate an insulin dose to be delivered by said insulin pump based on said received measurement; assess the validity of the status of the apparatus; and send a command to said insulin pump to deliver said calculated insulin dose, dependent on said assessing step confirming that the status is valid, wherein said apparatus is configured to operate in open-loop mode wherein said insulin pump is configured to deliver a preset dose of insulin unless said processor sends a command to said insulin pump so that said apparatus is configured to operate in closed-loop mode and wherein a said command sent to said insulin pump is valid only for a predetermined time interval so that if no further commands are sent to said insulin pump during said predetermined time interval, said insulin pump reverts to said open-loop mode delivering said preset dose of insulin at the end of said predetermined time interval.