Hmmmm hard call to make there.

13 is old for a cat but not ancient (Dusty is 16 1/2).

Being on pred full time will eventually do her in, but if it makes her time here shorter but more comfortable it seems worth it (Dusty will eventually have to go on Pred at some point also)

If it were Dusty I'd probably base it on how well she was doing at the moment, then weigh that with how stressful having the tests done on her would be.

Dusty has had a dentistry and blood work done this past Feb. She doesn't like it, however her stress never seems to cause her any health problems either. She just sleeps even more than usual for the day, but is right back to her normal self by the next day.

Whatever you decide to do with your kitty, I wish you the best.