Hi and welcome to the forum, corticosteroids are well known for raising blood glucose (gb) levels, I was on them long term before being diagnosed with T.2 diabetes.
When you see your doctor tomorrow he/she will no doubt prescribe medication to help get your levels down, you can help these drugs by cutting back on your consumption of carbohydrates especially those in things like Potato, bread, rice and pasta.
All carbohydrates turn to sugar (glucose) in our stomachs and that glucose then enters our blood streams via the intestines. Steroids cause high insulin resistance so your bodies own insulin wont be able to utilise the glucose in your blood which is why your levels have risen.
High glucose levels will be the cause of your tiredness and should recede as your levels start to drop again and as this happens you should start to feel your old self again.
It may be helpful for you to read the information given here to newly diagnosed diabetics even though you may not diabetic, fingers crossed
. You will find that information here, just click this link =
viewtopic.php?f=20&t=17088
Good luck at the docs tomorrow and I hope all goes well, and try not to worry too much before hand