Diabetes is not a contagious disease & it won't lead to any medical inadmissibility. Check the below thread.
http://www.canadavisa.com/canada-immigration-discussion-board/diabetes-patient-clear-medical-exam-plz-help-t55067.0.html
http://www.canada-city.ca/canada-immigration/posting.php?messageid=23012
No Diabetes is not a viral diese and do nt effect any other.........and it also do nt have heavy cost on Canadian medical treatment.........do nt worry it does not lead to inadmissibility...........