Cortisol test drug

Hello all. I have a dexamethasone suppressant test that starts tonight. I have a 1 mg of the dexamethasone and I have to take it tonight at 11 and get the blood drawn in the morning. Any of you have this test and if so, any side effects or anything that seemed to trigger a MAV episode? I’m a little wary as last time I took a corticosteroid, I had the worst insomnia and what I could only describe as roid rage in my life. This was years ago before I got sick but still. I’m going to need my sleep or I’ll be a disaster trying to drive to the clinic.