Prednisone jacks blood sugar as does the presence of Cortisol

The Cortisol causes excess sugar release from the Liver (stored sugar) and the Steroid prevents the muscles from properly absorbing sugar (and they are big sugar hogs as far as most of our blood sugar usage) as well as reducing (natural) insulin production

Quite a bit to overcome. An Endocrinologist would be the best doctor to try and help manage the Diabetes with the other condition(s)

When a more urgent condition must be treated sometimes the Diabetes has to take a back seat even though the longer term effect of not treating may become a problem - sometimes there are only bad choices and the best bad choice has to be made