Any kind of stress which may be due to some intercurent illness, as the case in your father, sugar tends to run high. This can be managed by altering the dose of  insulin.  But again there are certain insulin which tend to cause more fluctuations that others. Please let me know which insulin he is taking and I will advise accordingly.  I would get you father's cough and temperature investigated properly at this stage. Once that settles, sugar levels likely to fall in place as well.