Steroids are a stress hormone. Normally, when your body makes them, it's a signal to your liver to dump extra glucose because you need energy for either fight or flight. When you get an injection, your body can't tell the difference between natural occuring steroids and the injected kind, so.... Your liver'll dump. Probably for a few days. Keep an eye on your bloodsugar levels. Last time I had a shot I went up to nine, but it came back down again. If you go higher, say, 10 or 15, something like that, and it doesn't come down, get in touch with your GP.