I am not a medical professional but what I know about Addison's Disease is that everyone's body metabolizes hydrocortisone differently. There doesn't appear to be clearcut guidelines out in the world on this issue, so I would discuss the Addison's issue with your GI doctor and ask that he consult with your endo for proper guidance on how to proceed. There should be a discussion with you once the plan is established so you can ask any questions and express any concerns before you begin the prep, I think it's wise to be sure that there is a plan to have an emergency injection ready during the procedure in the event you need it.

It's surprising that you haven't been given an RX for an emergency injection kit. I would call the endo's nurse and request one. I hope this helps.

What are the opinions regarding extra cortisone, maybe even a drip, during prep for and during a colonoscopy?  Some countries talk about the need for a drip in either the prep, the procedure or both.
Also most suggest that even without a drip that the doctor should be prepared to administer an emergency injection.  I have been hypopit since 2012 and even though I've been to my local endocrinologist, Blevins at UCSF and Fleseriu at OHSU none of them have given me a prescription for an emergency injection.  I've been told I need one but after I leave the appointments I realize that, once again I am short a prescription.  My local pharmacist isn't  even aware of these injection kits.
I am 69, tested positive with the cologuard, had a colonoscopy ten years ago with some 'abnormal/pre-cancerous polyps, but I'm not sure the risks of prep and the procedure are worth the small chance of me getting colon cancer before I die of complications of hypopit.  Plus the endocrinologists around the world seem to have very different opinions.
Anyone know anything about this topic?