At what age does a dog become geriatric?

Sorry to here that you are typing in this question, but my dog,Iris, is this way to she is eight years old and is very sick she was born in 2003

and she has been through onecar crash and came home when my little brother was born and she has been through all of my three siblings and she has still made to this day.she is very sick she is weak and does not eat or drink,her nose gets very dry with bugars on them and does not move as much and hides underneath the house and all four of us are very lucky to have her and she is breathing very hard she is like panting for air but us six in our family need some advise for Iris!Please help us four with our baby girl...........thank you so much for writing below and please help me.Good Luck with yours, too!